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The periodic table, elements being denoted by their symbols

Chemical symbols are the abbreviations used in chemistry, mainly for chemical elements; but also for functional groups, chemical compounds, and other entities. Element symbols for chemical elements, also known as atomic symbols, normally consist of one or two letters from the Latin alphabet and are written with the first letter capitalised.

History

[edit]

Earlier symbols for chemical elements stem from classical Latin and Greek words. For some elements, this is because the material was known in ancient times, while for others, the name is a more recent invention. For example, Pb is the symbol for lead (plumbum in Latin); Hg is the symbol for mercury (hydrargyrum in Greek); and He is the symbol for helium (a Neo-Latin name) because helium was not known in ancient Roman times. Some symbols come from other sources, like W for tungsten (Wolfram in German) which was not known in Roman times.

A three-letter temporary symbol may be assigned to a newly synthesized (or not yet synthesized) element. For example, "Uno" was the temporary symbol for hassium (element 108) which had the temporary name of unniloctium, based on the digits of its atomic number. There are also some historical symbols that are no longer officially used.

Extension of the symbol

[edit]
Annotated example of an atomic symbol

In addition to the letters for the element itself, additional details may be added to the symbol as superscripts or subscripts a particular isotope, ionization, or oxidation state, or other atomic detail.[1] A few isotopes have their own specific symbols rather than just an isotopic detail added to their element symbol.

Attached subscripts or superscripts specifying a nuclide or molecule have the following meanings and positions:

  • The nucleon number (mass number) is shown in the left superscript position (e.g., 14N). This number defines the specific isotope. Various letters, such as "m" and "f" may also be used here to indicate a nuclear isomer (e.g., 99mTc). Alternately, the number here can represent a specific spin state (e.g., 1O2). These details can be omitted if not relevant in a certain context.
  • The proton number (atomic number) may be indicated in the left subscript position (e.g., 64Gd). The atomic number is redundant to the chemical element, but is sometimes used to emphasize the change of numbers of nucleons in a nuclear reaction.
  • If necessary, a state of ionization or an excited state may be indicated in the right superscript position (e.g., state of ionization Ca2+).
  • The number of atoms of an element in a molecule or chemical compound is shown in the right subscript position (e.g., N2 or Fe2O3). If this number is one, it is normally omitted - the number one is implicitly understood if unspecified.
  • A radical is indicated by a dot on the right side (e.g., Cl• for a neutral chlorine atom). This is often omitted unless relevant to a certain context because it is already deducible from the charge and atomic number, as generally true for nonbonded valence electrons in skeletal structures.

Many functional groups also have their own chemical symbol, e.g. Ph for the phenyl group, and Me for the methyl group.

A list of current, dated, as well as proposed and historical signs and symbols is included here with its signification. Also given is each element's atomic number, atomic weight, or the atomic mass of the most stable isotope, group and period numbers on the periodic table, and etymology of the symbol.

Symbols for chemical elements

[edit]
List of chemical elements
Z Symbol Name Origin of name[2][3]
1 H Hydrogen Greek elements hydro- and -gen, meaning 'water-forming'
2 He Helium Greek hḗlios, 'sun'
3 Li Lithium Greek líthos, 'stone'
4 Be Beryllium beryl, a mineral (ultimately from the name of Belur in southern India)
5 B Boron borax, a mineral (from Arabic bawraq)
6 C Carbon Latin carbo, 'coal'
7 N Nitrogen Greek nítron and -gen, meaning 'niter-forming'
8 O Oxygen Greek oxy- and -gen, meaning 'acid-forming'
9 F Fluorine Latin fluere, 'to flow'
10 Ne Neon Greek néon, 'new'
11 Na Sodium English soda (the symbol Na is derived from Neo-Latin natrium, coined from German Natron, 'natron')
12 Mg Magnesium Magnesia, a district of Eastern Thessaly in Greece
13 Al Aluminium alumina, from Latin alumen (gen. alumni), 'bitter salt, alum'
14 Si Silicon Latin silex, 'flint' (originally silicium)
15 P Phosphorus Greek phōsphóros, 'light-bearing'
16 S Sulfur Latin sulphur, 'brimstone'
17 Cl Chlorine Greek chlōrós, 'greenish yellow'
18 Ar Argon Greek argós, 'idle' (because of its inertness)
19 K Potassium Neo-Latin potassa, 'potash' (the symbol K is derived from Latin kalium)
20 Ca Calcium Latin calx, 'lime'
21 Sc Scandium Latin Scandia, 'Scandinavia'
22 Ti Titanium Titans, the sons of the Earth goddess of Greek mythology
23 V Vanadium Vanadis, an Old Norse name for the Scandinavian goddess Freyja
24 Cr Chromium Greek chróma, 'colour'
25 Mn Manganese corrupted from magnesia negra; see Magnesium
26 Fe Iron English word (the symbol Fe is derived from Latin ferrum)
27 Co Cobalt German Kobold, 'goblin'
28 Ni Nickel Nickel, a mischievous sprite of German miner mythology
29 Cu Copper English word, from Latin cuprum, from Ancient Greek Kýpros 'Cyprus'
30 Zn Zinc Most likely from German Zinke, 'prong' or 'tooth', though some suggest Persian sang, 'stone'
31 Ga Gallium Latin Gallia, 'France'
32 Ge Germanium Latin Germania, 'Germany'
33 As Arsenic French arsenic, from Greek arsenikón 'yellow arsenic' (influenced by arsenikós, 'masculine' or 'virile'), from a West Asian wanderword ultimately from Old Iranian *zarniya-ka, 'golden'
34 Se Selenium Greek selḗnē, 'moon'
35 Br Bromine Greek brômos, 'stench'
36 Kr Krypton Greek kryptós, 'hidden'
37 Rb Rubidium Latin rubidus, 'deep red'
38 Sr Strontium Strontian, a village in Scotland
39 Y Yttrium Ytterby, a village in Sweden
40 Zr Zirconium zircon, a mineral
41 Nb Niobium Niobe, daughter of king Tantalus from Greek mythology
42 Mo Molybdenum Greek molýbdaina, 'piece of lead', from mólybdos, 'lead'
43 Tc Technetium Greek tekhnētós, 'artificial'
44 Ru Ruthenium Neo-Latin Ruthenia, 'Russia'
45 Rh Rhodium Greek rhodóeis, 'rose-coloured', from rhódon, 'rose'
46 Pd Palladium the asteroid Pallas, considered a planet at the time
47 Ag Silver English word (The symbol derives from Latin argentum)
48 Cd Cadmium Neo-Latin cadmia, from King Kadmos
49 In Indium Latin indicum, 'indigo' (colour found in its spectrum)
50 Sn Tin English word (The symbol derives from Latin stannum)
51 Sb Antimony Latin antimonium, the origin of which is uncertain: folk etymologies suggest it is derived from Greek antí ('against') + mónos ('alone'), or Old French anti-moine, 'Monk's bane', but it could plausibly be from or related to Arabic ʾiṯmid, 'antimony', reformatted as a Latin word. (The symbol derives from Latin stibium 'stibnite'.)
52 Te Tellurium Latin tellus, 'the ground, earth'
53 I Iodine French iode, from Greek ioeidḗs, 'violet'
54 Xe Xenon Greek xénon, neuter form of xénos 'strange'
55 Cs Caesium Latin caesius, 'sky-blue'
56 Ba Barium Greek barýs, 'heavy'
57 La Lanthanum Greek lanthánein, 'to lie hidden'
58 Ce Cerium the dwarf planet Ceres, considered a planet at the time
59 Pr Praseodymium Greek prásios dídymos, 'green twin'
60 Nd Neodymium Greek néos dídymos, 'new twin'
61 Pm Promethium Prometheus of Greek mythology
62 Sm Samarium samarskite, a mineral named after Colonel Vasili Samarsky-Bykhovets, Russian mine official
63 Eu Europium Europe
64 Gd Gadolinium gadolinite, a mineral named after Johan Gadolin, Finnish chemist, physicist and mineralogist
65 Tb Terbium Ytterby, a village in Sweden
66 Dy Dysprosium Greek dysprósitos, 'hard to get'
67 Ho Holmium Neo-Latin Holmia, 'Stockholm'
68 Er Erbium Ytterby, a village in Sweden
69 Tm Thulium Thule, the ancient name for an unclear northern location
70 Yb Ytterbium Ytterby, a village in Sweden
71 Lu Lutetium Latin Lutetia, 'Paris'
72 Hf Hafnium Neo-Latin Hafnia, 'Copenhagen' (from Danish havn)
73 Ta Tantalum King Tantalus, father of Niobe from Greek mythology
74 W Tungsten Swedish tung sten, 'heavy stone' (The symbol is from wolfram, the old name of the tungsten mineral wolframite)
75 Re Rhenium Latin Rhenus, 'the Rhine'
76 Os Osmium Greek osmḗ, 'smell'
77 Ir Iridium Iris, the Greek goddess of the rainbow
78 Pt Platinum Spanish platina, 'little silver', from plata 'silver'
79 Au Gold English word (The symbol derives from Latin aurum)
80 Hg Mercury Mercury, Roman god of commerce, communication, and luck, known for his speed and mobility (The symbol is from the element's Latin name hydrargyrum, derived from Greek hydrárgyros, 'water-silver')
81 Tl Thallium Greek thallós, 'green shoot or twig'
82 Pb Lead English word (The symbol derives from Latin plumbum)
83 Bi Bismuth German Wismut, from weiß Masse 'white mass', unless from Arabic
84 Po Polonium Latin Polonia, 'Poland' (the home country of Marie Curie)
85 At Astatine Greek ástatos, 'unstable'
86 Rn Radon radium
87 Fr Francium France
88 Ra Radium French radium, from Latin radius, 'ray'
89 Ac Actinium Greek aktís, 'ray'
90 Th Thorium Thor, the Scandinavian god of thunder
91 Pa Protactinium proto- (from Greek prôtos, 'first, before') + actinium, which is produced through the radioactive decay of protactinium
92 U Uranium Uranus, the seventh planet in the Solar System
93 Np Neptunium Neptune, the eighth planet in the Solar System
94 Pu Plutonium the dwarf planet Pluto, considered the ninth planet in the Solar System at the time
95 Am Americium The Americas, as the element was first synthesised on the continent, by analogy with europium
96 Cm Curium Pierre Curie and Marie Curie, French physicists and chemists
97 Bk Berkelium Berkeley, California, where the element was first synthesised, by analogy with terbium
98 Cf Californium California, where the element was first synthesised
99 Es Einsteinium Albert Einstein, German physicist
100 Fm Fermium Enrico Fermi, Italian physicist
101 Md Mendelevium Dmitri Mendeleev, Russian chemist and inventor who proposed the periodic table
102 No Nobelium Alfred Nobel, Swedish chemist and engineer
103 Lr Lawrencium Ernest O. Lawrence, American physicist
104 Rf Rutherfordium Ernest Rutherford, New Zealand chemist and physicist
105 Db Dubnium Dubna, Russia, where the Joint Institute for Nuclear Research is located
106 Sg Seaborgium Glenn T. Seaborg, American chemist
107 Bh Bohrium Niels Bohr, Danish physicist
108 Hs Hassium Neo-Latin Hassia, 'Hesse' (a state in Germany)
109 Mt Meitnerium Lise Meitner, Austrian physicist
110 Ds Darmstadtium Darmstadt, Germany, where the element was first synthesised
111 Rg Roentgenium Wilhelm Conrad Röntgen, German physicist
112 Cn Copernicium Nicolaus Copernicus, Polish astronomer
113 Nh Nihonium Japanese Nihon, 'Japan' (where the element was first synthesised)
114 Fl Flerovium Flerov Laboratory of Nuclear Reactions, part of JINR, where the element was synthesised; itself named after Georgy Flyorov, Russian physicist
115 Mc Moscovium Moscow Oblast, Russia, where the element was first synthesised
116 Lv Livermorium Lawrence Livermore National Laboratory in Livermore, California, which collaborated with JINR on its synthesis
117 Ts Tennessine Tennessee, United States
118 Og Oganesson Yuri Oganessian, Russian physicist

Symbols and names not currently used

[edit]

The following is a list of symbols and names formerly used or suggested for elements, including symbols for placeholder names and names given by discredited claimants for discovery.

Symbol Name Atomic
number		 Notes Why not
used		 Refs
A Argon 18 A used for Argon until 1957. Current symbol is Ar. [nb 1] [4]
Ab Alabamine 85 Discredited claim to discovery of astatine. [nb 2] [5][6]
Ad Aldebaranium 70 Former name for ytterbium. [nb 2]
Ah Anglohelvetium 85 Discredited claim to discovery of astatine. [nb 2] [7]
Ak Alkalinium 87 Discredited claim to discovery of francium. [nb 2] [5]
Am Alabamine 85 Discredited claim to discovery of astatine. The symbol Am is now used for americium. [nb 2] [5][6]
An Athenium 99 Proposed name for einsteinium. [nb 3]
Ao Ausonium 93 Discredited claim to discovery of neptunium. [nb 2] [5]
At Austriacum 84 Discredited claim to discovery of polonium. The symbol At is now used for astatine. [nb 2]
Az Azote 7 Former name for nitrogen. [nb 1]
Bo Bohemium 93 Discredited claim to discovery of neptunium. [nb 2]
Bo Boron 5 Current symbol is B. [nb 1]
Bv Brevium 91 Former name for protactinium-234. [nb 1]
Bz Berzelium 90 Baskerville wrongly believed berzelium was a new element. Was actually thorium. [7]
Cb Columbium 41 Former name for niobium. [nb 1] [5][7]
Ch Chromium 24 Current symbol is Cr. [nb 1]
Cl Columbium 41 Former name for niobium. The symbol Cl is now used for chlorine. [nb 1]
Cm Catium 87 Proposed name for francium. The symbol Cm is now used for curium. [nb 3]
Cn Carolinium 90 Baskerville wrongly believed carolinium to be a new element. Was actually thorium. The symbol Cn is now used for copernicium. [7]
Cp Cassiopeium 71 Former name for lutetium. [nb 1]
Cp Copernicium 112 Current symbol is Cn. [nb 1]
Ct Celtium 72 Discredited claim to discovery of hafnium. [nb 2]
Ct Centurium 100 Proposed name for fermium. [nb 3]
Cy Cyclonium 61 Proposed name for promethium. [nb 3]
D Didymium 59/60 Mixture of the elements praseodymium and neodymium. Mosander wrongly believed didymium to be an element. [8]
Da Davyum 43 Discredited claim to discovery of technetium. [nb 2] [5]
Db Dubhium 69 Eder wrongly believed dubhium to be a new element. Was actually thulium. The symbol Db is now used for dubnium.
Db Dubnium 104 Proposed name for rutherfordium. The symbol and name were instead used for element 105. [nb 1][nb 3] [5]
Dc Decipium 62 Delafontaine wrongly believed decipium to be a new element. Was actually samarium.
Dc Dvicaesium 87 Name given by Mendeleev to an as of then undiscovered element. When discovered, francium closely matched the prediction. [nb 3][nb 4]
De Denebium 69 Eder wrongly believed denebium to be a new element. Was actually thulium.
Di Didymium 59/60 Mixture of the elements praseodymium and neodymium. Mosander wrongly believed didymium to be an element. [8]
Do Dor 85 Discredited claim to discovery of astatine made by Horia Hulubei and Yvette Cauchois. [nb 2] [7]
Dn Dubnadium 118 Proposed name for oganesson. [nb 3]
Dp Decipium 62 Delafontaine wrongly believed decipium to be a new element. Was actually samarium.
Ds Dysprosium 66 Current symbol is Dy. The symbol Ds is now used for darmstadtium. [nb 1]
Dt Dvitellurium 84 Name given by Mendeleev to an as of then undiscovered element. When discovered, polonium closely matched the prediction. [nb 3][nb 4]
E Einsteinium 99 Current symbol is Es. [nb 1]
E Erbium 68 Current symbol is Er. [nb 1]
Ea Ekaaluminium 31 Name given by Mendeleev to an as of then undiscovered element. When discovered, gallium closely matched the prediction. [nb 3][nb 4]
Eb Ekaboron 21 Name given by Mendeleev to an as of then undiscovered element. When discovered, scandium closely matched the prediction. [nb 3][nb 4] [5]
Eb Erebodium 42 Alexander Pringle wrongly believed erebodium to be a new element. Was likely molybdenum. [7]
El Ekaaluminium 31 Name given by Mendeleev to an as of then undiscovered element. When discovered, gallium closely matched the prediction. [nb 3][nb 4] [5]
Em Ekamanganese 43 Name given by Mendeleev to an as of then undiscovered element. When discovered, technetium closely matched the prediction. [nb 3][nb 4] [5]
Em Emanation 86 Also called "radium emanation", the name was originally given by Friedrich Ernst Dorn in 1900.
In 1923, this element officially became radon (the name given at one time to 222Rn, an isotope identified in the decay chain of radium).		 [nb 1] [5]
Em Emanium 89 Alternate name formerly proposed for actinium. [nb 3]
Es Ekasilicon 32 Name given by Mendeleev to a then undiscovered element. When discovered, germanium closely matched the prediction.
The symbol Es is now used for einsteinium.		 [nb 3][nb 4] [5]
Hs Hesperium 94 Discredited claim to discovery of plutonium. The symbol Hs is now used for hassium. [nb 2] [5][7]
Et Ekatantalum 91 Name given by Mendeleev to an as of then undiscovered element. When discovered, protactinium closely matched the prediction. [nb 3][nb 4]
Ex Euxenium 72 Discredited claim to discovery of hafnium. [nb 2] [7]
Fa Francium 87 Current symbol is Fr. [nb 1]
Fl Florentium 61 Discredited claim to discovery of promethium. The symbol Fl is now used for flerovium. [nb 2]
Fl Fluorine 9 Current symbol is F. The symbol Fl is now used for flerovium. [nb 1]
Fr Florentium 61 Discredited claim to discovery of promethium. The symbol Fr is now used for francium. [nb 2] [5]
G Glucinium 4 Former name for beryllium. [nb 1]
Gh Ghiorsium 118 Discredited claim to discovery of oganesson. [nb 2]
Gl Glucinium 4 Former name for beryllium. [nb 1] [5]
Ha Hahnium 105 Proposed name for dubnium. [nb 3]
Hn Hahnium 108 Proposed name for hassium. [nb 3] [5]
Hv Helvetium 85 Discredited claim to discovery of astatine. [nb 2] [7]
Hy Mercury 80 Hy from the Greek hydrargyrum for "liquid silver". Current symbol is Hg. [nb 1] [4]
I Iridium 77 Current symbol is Ir. The symbol I is now used for iodine. [nb 1]
Ic Incognitium 65 Demarçay wrongly believed incognitium to be a new element. Was actually terbium mixed with gadolinium. [7]
Il Illinium 61 Discredited claim to discovery of promethium. [nb 2] [5]
Il Ilmenium 41/73 Mixture of the elements niobium and tantalum. R. Hermann wrongly believed ilmenium to be an element.
Io Ionium 65 Demarçay wrongly believed ionium to be a new element. Was actually terbium.
J Jodium 53 Former name for iodine. [nb 1]
Jg Jargonium 72 Discredited claim to discovery of hafnium. [nb 2] [5]
Jl Joliotium 105 Proposed name for dubnium. [nb 3] [5]
Jp Japonium 113 Proposed name for nihonium. [nb 3]
Ka Potassium 19 Current symbol is K. [nb 1]
Ku Kurchatovium 104 Proposed name for rutherfordium. [nb 3] [5]
L Lithium 3 Current symbol is Li. [nb 1]
Lw Lawrencium 103 Current symbol is Lr. [nb 1]
M Muriaticum 17 Former name for chlorine. [nb 1]
Ma Manganese 25 Current symbol is Mn. [nb 1]
Ma Masurium 43 Disputed claim to discovery of technetium. [nb 2] [5]
Md Mendelevium 97 Proposed name for berkelium. The symbol and name were later used for element 101. [nb 1][nb 3]
Ml Moldavium 87 Discredited claim to discovery of francium made by Horia Hulubei and Yvette Cauchois. [nb 2] [7]
Ms Magnesium 12 Current symbol is Mg. [nb 1]
Ms Masrium 88 Discredited claim to discovery of radium. [nb 2]
Ms Masurium 43 Disputed claim to discovery of technetium. [nb 2]
Ms Mosandrium 65 Smith wrongly believed mosandrium to be a new element. Was actually terbium.
Mv Mendelevium 101 Current symbol is Md. [nb 1]
Ng Norwegium 72 Discredited claim to discovery of hafnium. [nb 2]
No Norium 72 Discredited claim to discovery of hafnium. The symbol No is now used for nobelium. [nb 2]
Np Neptunium 91 Discredited claim to discovery of protactinium. The symbol and name were later used for element 93. [nb 2] [9]
Np Nipponium 43 Discredited claim to discovery of technetium. The symbol Np is now used for neptunium. [nb 2] [5]
Ns Nielsbohrium 105 Proposed name for dubnium. [nb 3] [5]
Ns Nielsbohrium 107 Proposed name for bohrium. [nb 3] [5]
Nt Niton 86 Former name for radon. [nb 1] [5]
Ny Neoytterbium 70 Former name for ytterbium. [nb 1]
P Lead 82 Current symbol is Pb. The symbol P is now used for phosphorus. [nb 1]
Pa Palladium 46 Current symbol is Pd. The symbol Pa is now used for protactinium. [nb 1]
Pe Pelopium 41 Former name for niobium. [nb 1]
Ph Phosphorus 15 Current symbol is P. [nb 1]
Pl Palladium 46 Current symbol is Pd. [nb 1]
Pm Polymnestum 33 Alexander Pringle wrongly believed polymnestum to be a new element. Was likely arsenic. The symbol Pm is now used for promethium. [7]
Po Potassium 19 Current symbol is K. The symbol Po is now used for polonium. [nb 1]
Pp Philippium 67 Delafontaine discovered a new element and named it philippium. Per Teodor Cleve isolated it and renamed it holmium. [7]
R Rhodium 45 Current symbol is Rh. (The symbol is now sometimes used for an alkyl group.) [nb 1]
Rd Radium 88 Current symbol is Ra. [nb 1]
Rf Rutherfordium 106 Proposed name for seaborgium. The symbol and name were instead used for element 104. [nb 1][nb 3] [5]
Ro Rhodium 45 Current symbol is Rh. [nb 1]
Sa Samarium 62 Current symbol is Sm. [nb 1] [5]
So Sodium 11 Current symbol is Na. [nb 1]
Sq Sequanium 93 Discredited claim to discovery of neptunium made by Horia Hulubei and Yvette Cauchois. [nb 2] [7]
St Antimony 51 Current symbol is Sb. [nb 1]
St Tin 50 Current symbol is Sn. [nb 1]
Tm Trimanganese 75 Name given by Mendeleev to an as of then undiscovered element. When discovered, rhenium closely matched the prediction. The symbol Tm is now used for thulium. [nb 3][nb 4]
Tn Tungsten 74 Current symbol is W. [nb 1]
Tr Terbium 65 Current symbol is Tb. [nb 1]
Tu Thulium 69 Current symbol is Tm. [nb 1]
Tu Tungsten 74 Current symbol is W. [nb 1]
Ur Uralium 75 Discredited claim to discovery of rhenium. [nb 2]
Ur Uranium 92 Current symbol is U. [nb 1]
Vc Victorium 64 Crookes wrongly believed victorium to be a new element. Was actually gadolinium.
Vi Victorium 64 Crookes wrongly believed victorium to be a new element. Was actually gadolinium.
Vi Virginium 87 Discredited claim to discovery of francium. [nb 2] [5]
Vm Virginium 87 Discredited claim to discovery of francium. [nb 2] [5]
Va Vanadium 23 Current symbol is V. [nb 1]
Wo Wolfram 74 Former name for tungsten. [nb 1]
X Xenon 54 Current symbol is Xe. The symbol X is now used for any halogen. [nb 1]
Yt Yttrium 39 Current symbol is Y. [nb 1] [5]

Systematic chemical symbols

[edit]

These symbols are based on systematic element names, which are now replaced by trivial (non-systematic) element names and symbols. Data is given in order of: atomic number, systematic symbol, systematic name; trivial symbol, trivial name.

When elements beyond oganesson (starting with ununennium, Uue, element 119), are discovered; their systematic name and symbol will presumably be superseded by a trivial name and symbol.

Alchemical symbols

[edit]
Main article: Alchemical symbols

The following ideographic symbols were used in alchemy to denote elements known since ancient times. Not included in this list are spurious elements, such as the classical elements fire and water or phlogiston, and substances now known to be compounds. Many more symbols were in at least sporadic use: one early 17th-century alchemical manuscript lists 22 symbols for mercury alone.[10]

Planetary names and symbols for the metals – the seven planets and seven metals known since Classical times in Europe and the Mideast – was ubiquitous in alchemy. The association of what are anachronistically known as planetary metals started breaking down with the discovery of antimony, bismuth and zinc in the 16th century. Alchemists would typically call the metals by their planetary names, e.g. "Saturn" for lead and "Mars" for iron; compounds of tin, iron and silver continued to be called "jovial", "martial" and "lunar"; or "of Jupiter", "of Mars" and "of the moon", through the 17th century. The tradition remains today with the name of the element mercury, where chemists decided the planetary name was preferable to common names like "quicksilver", and in a few archaic terms such as lunar caustic (silver nitrate) and saturnism (lead poisoning).[10]

Alchemical symbols for the modern elements
Symbol Element Atomic
number		 Notes
Phosphorus 15 (discovered late)
🜍 Sulfur 16 used by Newton
Manganese 25 late; used by Torbern Bergman (1775)
♂ Iron 26 classical planetary metal of Mars
🜶 Cobalt 27 late; used by Bergman
Nickel 28 late; used by Bergman (old positional variant of arsenic, previously used for regulus of sulfur)
Zinc 30 late; used by Bergman
♀ Copper 29 classical planetary metal of Venus
🜺 Arsenic 33
☾ Silver 47 classical planetary metal of the Moon
🜛
♃ Tin 50 classical planetary metal of Jupiter
♁ Antimony 51 the newly discovered "eighth metal" was given the symbol for the Earth, which was recognized as a planet by that time
Platinum 78 late; used by Bergman et al.: a compound of ☉ gold and ☾ silver
⛢ late; symbol invented for the newly discovered planet Uranus so that it could also be used for newly recognized platinum
🜚 Gold 79 classical variant
☉ medieval variant; planetary metal of the Sun
☿ Mercury 80 classical planetary metal of Mercury
♄ Lead 82 classical planetary metal of Saturn
♆ Bismuth 83 used by Newton
♉︎ used by Bergman

Daltonian symbols

[edit]
Dalton's symbols for the more common elements, as of 1806, and the relative weights he calculated. The symbols for magnesium and calcium ("lime") were replaced by 1808, and that for gold was simplified.

The following symbols were employed by John Dalton in the early 1800s as the periodic table of elements was being formulated. Not included in this list are symbols for compounds, such as certain rare-earth mineral blends. Modern alphabetic notation was introduced in 1814 by Jöns Jakob Berzelius; its precursor can be seen in Dalton's circled letters for the metals, especially in his augmented table from 1810.[11] A trace of Dalton's conventions also survives in ball-and-stick models of molecules, where balls for carbon are black and for oxygen red.

Daltonian symbols for the elements
Symbol Dalton's name Modern name Atomic
number		 Notes Refs
img. char.
☉ hydrogen 1 or ⊙ [12]
glucine beryllium 4 alchemical symbol for 'sugar' [13]
● carbone, carbon carbon 6 [12]
⦶ azote nitrogen/azote 7 alchemical symbol for niter [12]
○ oxygen 8 or ◯ [12]
⦷ soda sodium 11 [12]
⊛ magnesia magnesium 12 alchemical symbol for magnesia [12]
alumine aluminium 13 (4 dots) [12]
🟕 silex silicon 14 [13]
phosphorus 15 (3 radii) [12]
🜨 sulphur 16 [12]
potash potassium 19 (3 vertical lines) [12]
⦾ lime calcium 20 or ◎ [12]
titanium 22 (enclosing circle) Tit⃝ [13]
manganese 25 (enclosing circle) Ma⃝ [13]
Ⓘ iron 26 [12]
Ⓝ nickel 28 [12]
cobalt 27 (enclosing circle) Cob⃝ [13]
Ⓒ copper 29 (black letter in red circle) [12]
Ⓩ zinc 30 [12]
arsenic 33 (enclosing circle) Ar⃝ [13]
strontian strontium 38 (4 ticks) [12]
⊕︀︀ yttria yttrium 39 (plus does not touch circle) [13]
zircone zirconium 40 (vertical zigzag) [13]
Ⓢ silver 47 [12]
Ⓣ tin 50 [13]
antimony 51 (enclosing circle) An⃝ [13]
barytes barium 56 (6 ticks) [12]
cerium 58 (enclosing circle) Ce⃝ [13]
tungsten 74 (enclosing circle) Tu⃝ [13]
Ⓟ platina platinum 78 (black letter in red circle) [12]
Ⓖ gold 79 [12]
mercury 80 (dotted inside perimeter) [12]
Ⓛ lead 82 [12]
Ⓑ bismuth 83 [13]
Ⓤ uranium 92 [13]

Symbols for named isotopes

[edit]

The following is a list of isotopes which have been given unique symbols. This is not a list of current systematic symbols (in the uAtom form); such a list can instead be found in Template:Navbox element isotopes. The symbols for isotopes of hydrogen, deuterium (D) and tritium (T), are still in use today, as is thoron (Tn) for radon-220 (though not actinon; An usually instead means a generic actinide). Heavy water and other deuterated solvents are commonly used in chemistry, and it is convenient to use a single character rather than a symbol with a subscript in these cases. The practice also continues with tritium compounds. When the name of the solvent is given, a lowercase d is sometimes used. For example, d6-benzene or C6D6 can be used instead of C6[2H6].[14]

The symbols for isotopes of elements other than hydrogen and radon are no longer used in the scientific community. Many of these symbols were designated during the early years of radiochemistry, and several isotopes (namely those in the decay chains of actinium, radium, and thorium) bear placeholder names using the early naming system devised by Ernest Rutherford.[15]

Symbol Name Atomic
number		 Origin of symbol
Ac Actinium 89 From Greek aktinos. Name restricted at one time to 227Ac, an isotope of actinium. This named isotope later became the official name for element 89.
AcA Actinium A 84 From actinium and A. Placeholder name given at one time to 215Po, an isotope of polonium identified in the decay chain of actinium.
AcB Actinium B 82 From actinium and B. Placeholder name given at one time to 211Pb, an isotope of lead identified in the decay chain of actinium.
AcC Actinium C 83 From actinium and C. Placeholder name given at one time to 211Bi, an isotope of bismuth identified in the decay chain of actinium.
AcC′ Actinium C′ 84 From actinium and C′. Placeholder name given at one time to 211Po, an isotope of polonium identified in the decay chain of actinium.
AcC″ Actinium C″ 81 From actinium and C″. Placeholder name given at one time to 207Tl, an isotope of thallium identified in the decay chain of actinium.
AcK Actinium K 87 Name given at one time to 223Fr, an isotope of francium identified in the decay chain of actinium.
AcU Actino-uranium 92 Name given at one time to 235U, an isotope of uranium.
AcX Actinium X 88 Name given at one time to 223Ra, an isotope of radium identified in the decay chain of actinium.
An Actinon 86 From actinium and emanation. Name given at one time to 219Rn, an isotope of radon identified in the decay chain of actinium.
D Deuterium 1 From the Greek deuteros. Name given to 2H.
Io Ionium 90 Name given to 230Th, an isotope of thorium identified in the decay chain of uranium.
MsTh1 Mesothorium 1 88 Name given at one time to 228Ra, an isotope of radium.
MsTh2 Mesothorium 2 89 Name given at one time to 228Ac, an isotope of actinium.
Pa Protactinium 91 From the Greek protos and actinium. Name restricted at one time to 231Pa, an isotope of protactinium. This named isotope later became the official name for element 91.
Ra Radium 88 From the Latin radius. Name restricted at one time to 226Ra, an isotope of radium. This named isotope later became the official name for element 88.
RaA Radium A 84 From radium and A. Placeholder name given at one time to 218Po, an isotope of polonium identified in the decay chain of radium.
RaB Radium B 82 From radium and B. Placeholder name given at one time to 214Pb, an isotope of lead identified in the decay chain of radium.
RaC Radium C 83 From radium and C. Placeholder name given at one time to 214Bi, an isotope of bismuth identified in the decay chain of radium.
RaC′ Radium C′ 84 From radium and C′. Placeholder name given at one time to 214Po, an isotope of polonium identified in the decay chain of radium.
RaC″ Radium C″ 81 From radium and C″. Placeholder name given at one time to 210Tl, an isotope of thallium identified in the decay chain of radium.
RaD Radium D 82 From radium and D. Placeholder name given at one time to 210Pb, an isotope of lead identified in the decay chain of radium.
RaE Radium E 83 From radium and E. Placeholder name given at one time to 210Bi, an isotope of bismuth identified in the decay chain of radium.
RaE″ Radium E″ 81 From radium and E″. Placeholder name given at one time to 206Tl, an isotope of thallium identified in the decay chain of radium.
RaF Radium F 84 From radium and F. Placeholder name given at one time to 210Po, an isotope of polonium identified in the decay chain of radium.
RdAc Radioactinium 90 Name given at one time to 227Th, an isotope of thorium.
RdTh Radiothorium 90 Name given at one time to 228Th, an isotope of thorium.
Rn Radon 86 From radium and emanation. Name restricted at one time to 222Rn, an isotope of radon identified in the decay chain of radium. This named isotope later became the official name for element 86 in 1923.
T Tritium 1 From the Greek tritos. Name given to 3H.
Th Thorium 90 After Thor. Name restricted at one time to 232Th, an isotope of thorium. This named isotope later became the official name for element 90.
ThA Thorium A 84 From thorium and A. Placeholder name given at one time to 216Po, an isotope of polonium identified in the decay chain of thorium.
ThB Thorium B 82 From thorium and B. Placeholder name given at one time to 212Pb, an isotope of lead identified in the decay chain of thorium.
ThC Thorium C 83 From thorium and C. Placeholder name given at one time to 212Bi, an isotope of bismuth identified in the decay chain of thorium.
ThC′ Thorium C′ 84 From thorium and C′. Placeholder name given at one time to 212Po, an isotope of polonium identified in the decay chain of thorium.
ThC″ Thorium C″ 81 From thorium and C″. Placeholder name given at one time to 208Tl, an isotope of thallium identified in the decay chain of thorium.
ThX Thorium X 88 Name given at one time to 224Ra, an isotope of radium identified in the decay chain of thorium.
Tn Thoron 86 From thorium and emanation. Name given to 220Rn, an isotope of radon identified in the decay chain of thorium.
UI Uranium I 92 Name given at one time to 238U, an isotope of uranium.
UII Uranium II 92 Name given at one time to 234U, an isotope of uranium.
UX1 Uranium X1 90 Name given at one time to 234Th, an isotope of thorium identified in the decay chain of uranium.
UX2 Uranium X2 91 Name given at one time to 234mPa, an isotope of protactinium identified in the decay chain of uranium.
UY Uranium Y 90 Name given at one time to 231Th, an isotope of thorium identified in the decay chain of uranium.
UZ Uranium Z 91 Name given at one time to 234Pa, an isotope of protactinium identified in the decay chain of uranium.

Other symbols

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See also: Skeletal formula § Pseudoelement symbols

General:

From organic chemistry:

From organometallic chemistry:

  • Fc, ferrocenyl: (C5H5)Fe(C5H4)
  • Fp, (Cyclopentadienyl)iron dicarbonyl: (C5H5)Fe(CO)2

Exotic atoms:

Hazard pictographs are another type of symbols used in chemistry.

See also

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Notes

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References

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Chemical symbol

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from Grokipedia
A chemical symbol is a concise, standardized notation of one or two letters, with the first letter uppercase, used to represent a chemical element in the periodic table and throughout chemical nomenclature. These symbols facilitate clear communication in scientific contexts, such as writing chemical formulas, equations, and reactions, and are derived primarily from the element's English or Latin name, though some reflect historical or discoverer preferences. Currently, there are 118 recognized elements, each assigned a unique symbol by the International Union of Pure and Applied Chemistry (IUPAC), ensuring global consistency in chemistry. The modern system of chemical symbols originated in the early 19th century, introduced by Swedish chemist Jöns Jacob Berzelius in 1814 through his publication "On the Chemical Signs, and the Method of Employing Them to Express Chemical Proportions." Berzelius proposed using the initial letter of each element's Latin name—such as "C" for carbon and "O" for oxygen—with a second lowercase letter added when needed to distinguish elements sharing the same initial, like "Ca" for calcium and "Cl" for chlorine. This replaced earlier, more cumbersome notations, including alchemical symbols and John Dalton's arbitrary circles and lines from the early 1800s, providing a simpler, alphabetic system that aligned with emerging atomic theory and allowed for the representation of compound proportions. Over time, the system evolved with the discovery of new elements, leading to IUPAC's formal role in standardization, as IUPAC was founded in 1919. Prior to official naming, provisional three-letter symbols (e.g., "Uup" for ununpentium) based on atomic number follow a systematic Latin-Greek root nomenclature established in 1979, such as "un-" for one, "bi-" for two, and so on. Once validated, discoverers propose permanent names and symbols, subject to IUPAC review and a five-month public consultation period, as seen with recent additions like nihonium (Nh) for element 113 in 2016. This process ensures symbols remain neutral, memorable, and tied to scientific or cultural significance, while avoiding duplication or national bias.

Fundamentals

Definition and Purpose

A chemical symbol is a one- or two-letter abbreviation that serves as a standardized notation for a chemical element, typically derived from the element's name in English, Latin, or another historical language. For instance, the symbol H denotes hydrogen, O represents oxygen, and Fe stands for iron (from the Latin ferrum). This system allows for precise identification of elements in scientific contexts. The first letter of every chemical symbol is uppercase, and any second letter is lowercase, ensuring uniformity and preventing confusion in written and printed materials. Examples include C for carbon (single letter) and Na for sodium (from the Latin natrium). These conventions promote readability and are universally adopted in chemistry. The purpose of chemical symbols is to enable concise representation of elements, facilitating efficient communication in chemical equations, molecular formulas, and nomenclature systems. By using these abbreviations, scientists can describe reactions and compounds briefly—such as H₂O for water—while maintaining clarity across global research and education. This shorthand is essential for balancing equations and analyzing compositions without lengthy descriptions. Chemical symbols emerged to address the need for standardization in the 18th and 19th centuries, as chemistry transitioned into a systematic discipline requiring consistent terminology for advancing discoveries and international collaboration.

Notation Rules

Chemical element symbols are standardized notations consisting of one or two letters, with the first letter always capitalized and any second letter in lowercase, ensuring clarity and uniformity in scientific communication. For example, the symbol for sodium is Na, where "N" is uppercase and "a" is lowercase. This convention is outlined in the IUPAC Nomenclature of Inorganic Chemistry to avoid ambiguity in distinguishing elements. The length of symbols is typically limited to one or two letters for the 118 currently recognized elements, derived primarily from their English or Latin names to promote international consistency; for instance, Fe represents iron (from Latin ferrum), while K denotes potassium (from Latin kalium). This derivation facilitates global use, as symbols are not always based on the vernacular name in every language. Provisional or systematic names for superheavy elements beyond atomic number 118, or previously undiscovered ones, employ three-letter symbols such as Uue for ununennium (hypothetical element 119), serving as placeholders until permanent names are approved. These three-letter exceptions are rare and strictly temporary, applied only during the discovery and verification process. In chemical formulas, element symbols represent individual atoms, and subscripts are used immediately following the symbol to denote the number of atoms of that element in the molecule or formula unit; if no subscript appears, it implies one atom. For water, the formula H₂O indicates two hydrogen atoms (H with subscript 2) bonded to one oxygen atom (O with no subscript). This notation follows the principle of juxtaposition of symbols with stoichiometric subscripts, forming the empirical or molecular formula that expresses the simplest ratio or exact composition of the compound.

Historical Evolution

Pre-Modern Symbols

Pre-modern chemical symbols emerged within the tradition of alchemy, spanning from the 7th to the 18th century, where they served as cryptic notations for substances, processes, and philosophical concepts rather than standardized identifiers for elements. These symbols originated in the Islamic Golden Age, particularly through the works of Jabir ibn Hayyan (c. 721–815 CE), who systematized alchemical practices and associated metals with planetary influences, laying the groundwork for symbolic representations that emphasized mystical and qualitative properties over empirical measurement. By the medieval period in Europe, alchemists had adopted and expanded these notations, using them to obscure knowledge from outsiders while facilitating communication among practitioners. Representative examples include the circle with a central dot (☉) for gold, symbolizing its association with the Sun and perfection; a crescent moon (☽) for silver, linked to lunar qualities; and an arrow-like sign (♂) for iron, tied to Mars and martial strength. The philosophical foundation of these symbols was rooted in ancient Greek cosmology, particularly Aristotle's theory of the four classical elements—earth, air, fire, and water—which alchemists viewed as the building blocks of matter, each embodying specific qualities like hot, cold, wet, and dry. Symbols for these elements were geometric and intuitive: an upward-pointing triangle (🜂) for fire, representing its rising, expansive nature; a downward-pointing triangle (🜄) for water, denoting descent and fluidity; a circle with a horizontal line above an upward triangle (🜁) for air; and a downward triangle with a horizontal line (🜃) for earth, signifying stability. This elemental framework intertwined with astrological associations, where the seven classical metals were mapped to the seven visible planets, reflecting a worldview that unified celestial, terrestrial, and spiritual realms. In the 16th century, Paracelsus (1493–1541), a pivotal figure in iatrochemistry—the fusion of alchemy and medicine—introduced the tria prima (three primes): sulfur (🜍, triangle with cross, embodying combustibility and the soul), mercury (☿, circle with cross, representing fluidity and spirit), and salt (🜔, square or circle with horizontal line, symbolizing fixity and body). Paracelsus and his iatrochemist followers employed these hieroglyphic-like signs in therapeutic contexts, viewing them as keys to understanding the microcosm of the human body and the macrocosm of nature, thereby shifting alchemy toward practical medical applications while retaining esoteric symbolism. By the 18th century, as alchemy transitioned into empirical chemistry amid the Enlightenment, symbols began evolving from esoteric icons to more descriptive tools, marking the onset of pre-modern standardization efforts. Chemists Jean-Henri Hassenfratz and Pierre-Auguste Adet proposed an ideographic system in the 1787 Méthode de nomenclature chimique, using basic geometric forms to categorize substances by properties: circles for metals, upright triangles for alkaline earths, inverted triangles for acids, and squares for salts, with modifiers like dots or lines to denote specific identities. This approach aimed to create intuitive, visual shorthand for chemical affinities and compositions, reflecting the influence of Antoine Lavoisier's nomenclature reforms, yet it proved overly complex and failed to gain broad acceptance due to its departure from simplicity. These innovations represented a bridge from alchemical mysticism to rational notation, paving the way for later 19th-century developments without fully supplanting traditional symbols in transitional texts.

Development of Modern Symbols

In the early 19th century, the rapid discovery of new elements following John Dalton's atomic theory of 1808 created a pressing need for a standardized shorthand in chemical notation, as earlier symbolic systems like Dalton's geometric circles became cumbersome for representing increasingly complex compounds and reactions. This proliferation, with elements doubling from around 30 known in 1800 to over 50 by the 1820s, underscored the demand for a concise, universal system to facilitate international communication among chemists. Swedish chemist Jöns Jacob Berzelius addressed this in a series of articles published in the Annals of Philosophy between 1813 and 1814, proposing a modern system of one- or two-letter symbols derived primarily from the Latin names of elements to ensure consistency across languages. For instance, he suggested "Fe" for iron (from ferrum), "Au" for gold (aurum), and "Na" for sodium (natrium), with the first letter capitalized and subsequent letters lowercase if needed; numbers as superscripts indicated atomic proportions in compounds, such as H²O for water. Berzelius's approach built on Antoine Lavoisier's nomenclature reforms while rejecting the visual symbols of predecessors, aiming for simplicity in writing chemical equations and formulas. The proposal faced initial resistance, notably from Dalton who preferred his own diagrammatic method, and from practical concerns like typesetting difficulties with superscripts, but it gained traction as its utility in analytical chemistry became evident. Language barriers posed another challenge, with national variations in element names (e.g., "potassium" in English versus "kalium" in Latin/German) leading to confusion, which Berzelius mitigated by standardizing on Latin roots to promote global adoption. By the 1820s, Berzelius's symbols were widely accepted in chemical literature across Europe, formalized in textbooks and journals, and forming the foundation for subsequent notations despite minor evolutions like the shift to subscripts in the late 19th century.

Current Element Symbols

IUPAC Standards

The International Union of Pure and Applied Chemistry (IUPAC), founded in 1919, holds the primary authority for standardizing the nomenclature of chemical elements, including the assignment and maintenance of their official symbols. This role ensures uniformity in scientific communication worldwide, with IUPAC collaborating with the International Union of Pure and Applied Physics (IUPAP) to verify discoveries before approving permanent names and symbols. Early formalization of symbol standards occurred in 1923, when IUPAC adopted specific symbols such as Rn for radon during its nomenclature efforts, laying the groundwork for subsequent updates. The assignment process for permanent symbols begins after a joint IUPAC/IUPAP working party confirms an element's discovery through rigorous evidence review. Discoverers then propose a name—typically derived from mythological concepts, scientific contributions, geographical locations, or properties—and a corresponding symbol, usually one or two letters taken from the name's Latin, English, or international form. IUPAC evaluates these proposals against established criteria, including uniqueness, to prevent conflicts with existing symbols or compounds; for instance, the initial suggestion of Fa for francium (element 87) was rejected in 1947 due to potential overlap with fluorine (F) and was replaced with Fr. Symbols must adhere to principles of brevity, favoring short forms for practicality in notation, and neutrality, ensuring they are internationally accessible without cultural bias or controversy. IUPAC periodically updates the periodic table to incorporate new elements, with recent approvals reflecting advances in superheavy element synthesis. In 2016, following confirmation of discoveries, IUPAC finalized symbols such as Nh for nihonium (element 113), Mc for moscovium (115), Ts for tennessine (117), and Og for oganesson (118), emphasizing eponymous naming for deceased scientists while maintaining symbol consistency. These updates are documented in IUPAC recommendations, ensuring the system evolves without redundancy or ambiguity.

Comprehensive List

The comprehensive list of the 118 recognized chemical elements is presented below, ordered by atomic number to align with their sequential discovery and placement in the periodic table. This organization facilitates quick reference and highlights the progression from light to heavy elements. The symbols, standardized by the International Union of Pure and Applied Chemistry (IUPAC), are one- or two-letter abbreviations derived primarily from the element's English, Latin, or other historical names, ensuring universality in scientific notation. Many symbols reflect etymological roots: for instance, H for hydrogen comes from the Greek "hydro" meaning water; Au for gold derives from the Latin "aurum"; W for tungsten originates from the German "wolfram"; and Fe for iron from the Latin "ferrum." These derivations often preserve historical or linguistic influences, as documented in authoritative compilations of element nomenclature.
Atomic NumberSymbolName
1HHydrogen
2HeHelium
3LiLithium
4BeBeryllium
5BBoron
6CCarbon
7NNitrogen
8OOxygen
9FFluorine
10NeNeon
11NaSodium
12MgMagnesium
13AlAluminium
14SiSilicon
15PPhosphorus
16SSulfur
17ClChlorine
18ArArgon
19KPotassium
20CaCalcium
21ScScandium
22TiTitanium
23VVanadium
24CrChromium
25MnManganese
26FeIron
27CoCobalt
28NiNickel
29CuCopper
30ZnZinc
31GaGallium
32GeGermanium
33AsArsenic
34SeSelenium
35BrBromine
36KrKrypton
37RbRubidium
38SrStrontium
39YYttrium
40ZrZirconium
41NbNiobium
42MoMolybdenum
43TcTechnetium
44RuRuthenium
45RhRhodium
46PdPalladium
47AgSilver
48CdCadmium
49InIndium
50SnTin
51SbAntimony
52TeTellurium
53IIodine
54XeXenon
55CsCaesium
56BaBarium
57LaLanthanum
58CeCerium
59PrPraseodymium
60NdNeodymium
61PmPromethium
62SmSamarium
63EuEuropium
64GdGadolinium
65TbTerbium
66DyDysprosium
67HoHolmium
68ErErbium
69TmThulium
70YbYtterbium
71LuLutetium
72HfHafnium
73TaTantalum
74WTungsten
75ReRhenium
76OsOsmium
77IrIridium
78PtPlatinum
79AuGold
80HgMercury
81TlThallium
82PbLead
83BiBismuth
84PoPolonium
85AtAstatine
86RnRadon
87FrFrancium
88RaRadium
89AcActinium
90ThThorium
91PaProtactinium
92UUranium
93NpNeptunium
94PuPlutonium
95AmAmericium
96CmCurium
97BkBerkelium
98CfCalifornium
99EsEinsteinium
100FmFermium
101MdMendelevium
102NoNobelium
103LrLawrencium
104RfRutherfordium
105DbDubnium
106SgSeaborgium
107BhBohrium
108HsHassium
109MtMeitnerium
110DsDarmstadtium
111RgRoentgenium
112CnCopernicium
113NhNihonium
114FlFlerovium
115McMoscovium
116LvLivermorium
117TsTennessine
118OgOganesson

Extended and Specialized Symbols

Isotope Notation

Isotope notation extends the standard chemical symbol of an element to specify a particular nuclide, primarily by incorporating the mass number. According to IUPAC recommendations, the nuclide symbol consists of the element's atomic symbol preceded by the mass number as a left superscript in Arabic numerals. For example, carbon-12 is denoted as 12C^{12}\text{C}, uranium-235 as 235U^{235}\text{U}, and hydrogen-2 as 2H^{2}\text{H}. The atomic number, which defines the element, is typically omitted from the notation since it is implied by the chemical symbol; however, it may be included as a left subscript for explicitness in certain contexts, such as 612C^{12}_{6}\text{C}. This format ensures clarity when distinguishing isotopes that share the same atomic number but differ in neutron count. For hydrogen isotopes, special single-letter symbols are permitted alongside the numerical notation: deuterium (hydrogen-2) may be represented as D or 2H^{2}\text{H}, and tritium (hydrogen-3) as T or 3H^{3}\text{H}, though these abbreviations are recommended only when no other nuclides are present in the formula to avoid ambiguity. The IUPAC Gold Book specifies that D refers specifically to the nuclide 2H^{2}\text{H}, with similar conventions for T. The primary purpose of isotope notation is to precisely identify and differentiate isotopes in fields like nuclear chemistry, where nuclear stability and reactions depend on mass number, and in mass spectrometry, where isotopic ratios are measured for elemental analysis. IUPAC guidelines emphasize consistent superscript placement to the left of the symbol in chemical formulas and names of isotopically modified compounds, ensuring interoperability in scientific communication; for instance, in molecular formulas, the notation integrates directly, as in 2H2O^{2}\text{H}_{2}\text{O} for heavy water.

Temporary and Systematic Symbols

In the systematic nomenclature established by the International Union of Pure and Applied Chemistry (IUPAC), elements with atomic numbers greater than 100 receive provisional names and three-letter symbols derived from their atomic numbers using Latin and Greek numerical roots, such as "nil" for 0, "un" for 1, "bi" for 2, up to "enn" for 9. These names end in "-ium" and are formed by combining roots for the hundreds, tens, and units digits of the atomic number; for instance, element 112 is named ununbium with symbol Uub, where "un-un-bi" corresponds to 1-1-2. This approach ensures a unique, unambiguous identifier for superheavy elements during the period between synthesis and official recognition. Upon verification of a discovery by a joint IUPAC/IUPAC Working Party, the temporary systematic name is replaced through a formal naming process where discoverers propose a permanent name—typically honoring a scientist, location, or mythological figure—and symbol, subject to IUPAC approval. For example, element 112 transitioned from ununbium (Uub) to copernicium (Cn) in 2010, commemorating astronomer Nicolaus Copernicus. Similarly, in 2016, elements 113, 115, 117, and 118 shed their provisional names—ununtrium (Uut), ununpentium (Uup), ununseptium (Uus), and ununoctium (Uuo)—for nihonium (Nh), moscovium (Mc), tennessine (Ts), and oganesson (Og), respectively, following confirmation of their syntheses. This systematic scheme extends to undiscovered or hypothetical elements beyond the current periodic table, such as element 119, provisionally designated ununennium (Uue). The primary rationale for these temporary designations is to facilitate scientific discourse without committing to a specific name until the element's properties are sufficiently confirmed and to prevent disputes over premature honorific naming. IUPAC's verification process, detailed in its standards, underscores this cautious approach by prioritizing empirical validation before permanence.

Obsolete Symbols

Alchemical and Early Representations

Alchemical symbols emerged in ancient Egypt, where hieroglyphic representations depicted metals and substances essential to metallurgical practices and religious rituals, such as the hieroglyph for gold (nebu, 𓋞, a beaded collar) symbolizing the flesh of the gods and divinity, and for silver (hedj, 𓋡). These early graphical notations evolved during the Hellenistic period in Alexandria around the 1st to 3rd centuries CE, integrating Greek philosophical concepts with Egyptian techniques, as seen in the works of Zosimos of Panopolis, who used rudimentary icons for processes like distillation. By the medieval era, Arabic alchemists like Jabir ibn Hayyan refined these into more systematic forms, which were then transmitted to Europe through translations in the 12th century, appearing in illuminated manuscripts that combined mystical and practical elements. In European alchemical texts from the 13th to 17th centuries, symbols became a coded visual language for substances, often linked to planetary correspondences reflecting astrological beliefs. A prominent example is the pseudonymous Basil Valentine, whose 15th- or early 16th-century writings, such as The Last Will and Testament (published 1624), featured comprehensive tables of these icons to denote metals, principles, and operations while concealing knowledge from outsiders. Common symbols included those for the seven classical metals tied to planets, as well as representations of the four elements and key principles like sulfur and salt. These were typically simple geometric figures drawn in manuscripts to facilitate secretive communication among practitioners. The following table illustrates 12 representative alchemical symbols, their traditional depictions, and corresponding modern chemical elements or concepts where applicable:
SymbolDepictionMeaning (Alchemical)Modern Equivalent
☉Circle with central dotGold (Sun)Au (Gold)
☽Crescent moonSilver (Moon)Ag (Silver)
☿Circle with cross below and semicircles aboveMercury (planet Mercury)Hg (Mercury)
♀Circle with cross belowCopper (Venus)Cu (Copper)
♂Circle with arrow pointing northeastIron (Mars)Fe (Iron)
♃Circle with semicircle belowTin (Jupiter)Sn (Tin)
♄Sickle or crescent with crossLead (Saturn)Pb (Lead)
△Upward-pointing triangleFire (element)Fire (conceptual)
▼Downward-pointing triangleWater (element)Water (conceptual)
🜁Upward triangle with horizontal lineAir (element)Air (conceptual)
🜃Downward triangle with horizontal lineEarth (element)Earth (conceptual)
🜍Triangle with cross belowSulfur (principle)S (Sulfur)
These icons, often hand-drawn with variations, emphasized qualitative attributes like volatility or fixity rather than precise composition. Alchemical symbols were inherently non-standardized, varying across regions, authors, and manuscripts due to their esoteric purpose, which aimed to protect trade secrets and philosophical insights from profane eyes. Unlike modern notations, they did not represent atomic structures but instead encoded qualitative properties, processes, and spiritual correspondences, leading to ambiguities that hindered consistent interpretation. This secrecy, rooted in guild traditions and fear of persecution, often rendered symbols context-dependent and opaque without initiatory knowledge. The legacy of these early representations lies in their influence on the visual and conceptual foundations of chemistry, providing an iconographic tradition that persisted into the 18th century for illustrating reactions and substances in texts by figures like Isaac Newton, who adapted them creatively in his laboratory notes. Planetary metal symbols, in particular, bridged alchemy with astronomy, embedding a symbolic heritage that informed early scientific diagrams and nomenclature.

Daltonian and Rejected Proposals

In 1808, John Dalton published his symbolic system for representing atoms and compounds in A New System of Chemical Philosophy, marking the first systematic attempt to visualize atomic theory through distinct icons. He depicted atoms as circles, with variations to distinguish elements: a plain circle for oxygen, a circle with a central dot for hydrogen, and a circle containing a line for nitrogen, for example. Compounds were shown as arrangements or superimpositions of these atomic symbols, such as two hydrogen symbols attached to one oxygen for water. Dalton's system, while innovative in linking symbols to relative atomic weights and molecular structures, proved impractical for widespread use due to challenges in printing the intricate diagrams and difficulties in scaling them for complex formulas. By the 1810s, it had largely been abandoned in favor of more streamlined notations, as chemists sought symbols that facilitated easier communication and calculation. Earlier, in 1787, Jean-Henri Hassenfratz and Pierre-Auguste Adet proposed an alternative system of numbered circles appended to Lavoisier's Méthode de Nomenclature Chimique, assigning sequential numbers within circles to elements like 1 for hydrogen and 8 for oxygen. This geometrical approach aimed to integrate with the new chemical nomenclature but was rejected for its complexity and lack of intuitiveness, failing to achieve broad adoption among chemists. Jöns Jacob Berzelius, in his early work around 1811–1812, experimented with pictorial representations influenced by Dalton's icons to denote atomic affinities and compound formations, such as using lines to indicate electrostatic bonds between atoms. However, he soon discarded these hieroglyph-like symbols as cumbersome, opting instead for an alphabetic system based on element names to ensure universality and simplicity in writing and printing. These rejected proposals shared common flaws, including limited ease of use for international collaboration and incompatibility with emerging printing technologies, ultimately paving the way for Berzelius' enduring letter-based conventions.

Additional Applications

Symbols in Formulas and Reactions

Chemical symbols form the basis of molecular formulas, which denote the elemental composition of compounds by juxtaposing symbols with subscripts to indicate the number of each type of atom present. According to IUPAC guidelines, element symbols in molecular formulas are typically arranged in alphabetical order or following conventional practice, with subscripts placed to the right and slightly below the symbol; for example, the formula for water is H₂O, representing two hydrogen atoms and one oxygen atom. This notation extends to diatomic elements, such as oxygen (O₂), and polyatomic ions or compounds like sulfuric acid (H₂SO₄). The use of parentheses is recommended for complex substructures, as in calcium nitrate, Ca(NO₃)₂, to clarify grouping. In chemical equations, symbols represent reactants and products, connected by reaction arrows to illustrate transformations while adhering to the law of conservation of mass. Balancing requires stoichiometric coefficients—whole numbers placed before formulas—to equalize atom counts on both sides; a classic example is the formation of water from hydrogen and oxygen: 2H2+O2→2H2O2\mathrm{H_2} + \mathrm{O_2} \rightarrow 2\mathrm{H_2O}, where coefficients ensure four hydrogen atoms and two oxygen atoms throughout. IUPAC specifies that equations should use a single arrow (→) for irreversible reactions and a double arrow (⇌) for equilibria, with states of matter denoted by symbols like (g) for gas appended to formulas. Structural representations in organic chemistry employ chemical symbols to convey atomic connectivity and bonding, often using lines to depict bonds between atoms while omitting hydrogens where implied by valence rules. For instance, ethane is simplified as CH₃-CH₃, with the hyphen representing a single bond. Radicals, indicating unpaired electrons, are marked with a superscript dot adjacent to the symbol, such as •CH₃ for the methyl radical or •OH for the hydroxyl radical. These conventions, outlined in IUPAC nomenclature, facilitate visualization of molecular architecture without exhaustive detail. However, chemical symbols in molecular formulas alone cannot distinguish isomers—compounds with identical elemental composition but differing atomic arrangements—necessitating supplementary notations like structural diagrams or stereodescriptors. For example, the formula C₄H₁₀ applies to both n-butane and isobutane, which exhibit distinct properties due to branched versus linear structures; IUPAC recommends systematic naming or graphical representations to resolve such ambiguities.

Variations Across Languages

Chemical element symbols, as standardized by the International Union of Pure and Applied Chemistry (IUPAC), form a universal notation system that transcends linguistic boundaries, ensuring consistency in scientific communication worldwide. Despite variations in element names across languages—such as iron in English, fer in French, and Eisen in German—the symbol Fe, derived from the Latin ferrum, remains unchanged in all contexts. This universality stems from the symbols' roots primarily in Latin and classical names, adopted internationally to avoid confusion in global research and education. Prior to IUPAC's standardization in the early 20th century, rare national or regional variants existed, reflecting local linguistic preferences. For instance, the symbol J was briefly used for iodine in some early German texts, based on the word Jod, before being unified as I. Such exceptions were short-lived and resolved through international agreement, emphasizing the shift toward a single, fixed set of symbols to support collaborative science. In educational materials, element names are often translated to match the local language, but the symbols themselves are invariably presented in their standard Latin-letter form to maintain precision and familiarity. For example, textbooks in Spanish use oro for gold but retain Au, aligning with the Latin aurum. This approach aids learners in non-English-speaking regions by bridging vernacular terms with the international nomenclature. The adoption of uniform symbols greatly facilitates cross-border research, enabling chemists from diverse linguistic backgrounds to share data without ambiguity, though minor challenges arise in non-Latin scripts where Latin letters must be transliterated or rendered directly. In languages like Chinese or Japanese, symbols appear alongside native character-based names, ensuring accessibility while preserving the global standard. Overall, this consistency underscores IUPAC's role in fostering a shared chemical language.

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