Symbol (chemistry)

See also: Hazard symbol

In chemistry, a symbol is a code for a chemical element. It is usually derived from the modern name of the element but for some elements it is derived from the name in Latin. For example, "He" is the symbol for helium (English name, not known in ancient Roman times), "Pb" for lead (plumbum in Latin), "Hg" for mercury (hydrargyrum in Greek), "W" for tungsten (wolfram in German, not known in Roman times). Only the first letter is capitalized.

Temporary symbols assigned to newly or not-yet synthesized elements use 3-letter symbols based on their atomic numbers. For example, "Uno" was the temporary symbol for hassium which had the temporary name of unniloctium and "Uuo" is the symbol for ununoctium (temporary name) with the atomic mass 118.

Chemical symbols may be modified by the use of prepended superscripts or subscripts to specify a particular isotope of an atom. Additionally, appended superscripts may be used to indicate the ionization or oxidation state of an element. They are widely used in chemistry and they have been officially chosen by the International Union of Pure and Applied Chemistry. There are also some historical symbols that are no longer officially used.

This is an example of an atomic symbol. The text boxes explain where the numbers are derived from.

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

• The nucleon number (mass number) is shown in the left superscript position (e.g., ¹⁴N)
• The proton number (atomic number) may be indicated in the left subscript position (e.g., ₆₄Gd)
• If necessary, a state of ionization or an excited state may be indicated in the right superscript position (e.g., state of ionization Ca²⁺). In astronomy, non-ionised atomic hydrogen is often known as "H I", and ionised hydrogen as "H II".
• 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)
• A radical is indicated by a dot on the right side (e.g., Cl· for a chloride radical)

In Chinese, each chemical element has a dedicated character, usually created for the purpose (see Chemical elements in East Asian languages). However, Latin symbols are also used, especially in formulas.

The periodic table, elements being denoted by their symbols

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

Symbol	Name	Etymology of symbol	Atomic number	Relative atomic mass	Group	Period	Metallic character
Ac	Actinium	Greek aktinos (ray)	89	&227[227]		7	Actinide
Ag	Silver	Latin argentum (silver)	47	&107.86822107.8682(2)	11	5	Transition metal
Al	Aluminium (aluminum)	Latin alumen (alum)	13	&026.9815386826.9815386(8)	13	3	Post-transition metal
Am	Americium	the Americas	95	&243[243]		7	Actinide
Ar	Argon	Greek argon (inert)	18	&039.948139.948(1)	18	3	Noble gas
As	Arsenic	Greek arsenikos (male)	33	&074.92160274.92160(2)	15	4	Metalloid
At	Astatine	Greek astatos (unstable)	85	&210[210]	17	6	Metalloid
Au	Gold	Latin aurum (gold)	79	&196.9665694196.966569(4)	11	6	Transition metal
B	Boron	borax	5	&010.811710.811(7)	13	2	Metalloid
Ba	Barium	Greek barys (density)	56	&137.3277137.327(7)	2	6	Alkaline earth metal
Be	Beryllium	beryl	4	&009.01218239.012182(3)	2	2	Alkaline earth metal
Bh	Bohrium	Niels Bohr	107	&264[264]	7	7	Transition metal
Bi	Bismuth	German wiss muth (white-mass), becoming bismuth in English	83	&208.980401208.98040(1)	15	6	Post-transition metal
Bk	Berkelium	Berkeley, California	97	&247[247]		7	Actinide
Br	Bromine	Greek bromos (stench)	35	&079.904179.904(1)	17	4	Diatomic nonmetal
C	Carbon	Latin carbo (charcoal)	6	&012.0107812.0107(8)	14	2	Polyatomic nonmetal
Ca	Calcium	Latin calx (lime)	20	&040.078440.078(4)	2	4	Alkaline earth metal
Cd	Cadmium	Greek kadmia (earth)	48	&112.4118112.411(8)	12	5	Transition metal
Ce	Cerium	Ceres	58	&140.1161140.116(1)		6	Lanthanide
Cf	Californium	State and University of California	98	&251[251]		7	Actinide
Cl	Chlorine	Greek chloros (green-yellow)	17	&035.453235.453(2)	17	3	Diatomic nonmetal
Cm	Curium	Pierre and Marie Curie and the traditional -um ending	96	&247[247]		7	Actinide
Cn	Copernicium	Nicolaus Copernicus	112	&285[285]	12	7	Transition metal
Co	Cobalt	German kobold	27	&058.933195558.933195(5)	9	4	Transition metal
Cr	Chromium	Greek chroma (color)	24	&051.9961651.9961(6)	6	4	Transition metal
Cs	Caesium (cesium)	Latin caesius (sky blue)	55	&132.90545192132.9054519(2)	1	6	Alkali metal
Cu	Copper	Latin Cuprum (Cyprus)	29	&063.546363.546(3)	11	4	Transition metal
Db	Dubnium	Dubna, Russia	105	&262[262]	5	7	Transition metal
Ds	Darmstadtium	Darmstadt, Germany	110	&271[271]	10	7	Unknown
Dy	Dysprosium	Greek dysprositos	66	&162.5001162.500(1)		6	Lanthanide
Er	Erbium	Ytterby, Sweden	68	&167.2593167.259(3)		6	Lanthanide
Es	Einsteinium	Albert Einstein	99	&252[252]		7	Actinide
Eu	Europium	Europe	63	&151.9641151.964(1)		6	Lanthanide
F	Fluorine	Latin fluo (flow)	9	&018.9984032518.9984032(5)	17	2	Diatomic nonmetal
Fe	Iron	Latin ferrum (iron)	26	&055.845255.845(2)	8	4	Transition metal
Fl	Flerovium	Flerov Laboratory of Nuclear Reactions	114	&289[289]	14	7	Unknown
Fm	Fermium	Enrico Fermi	100	&257[257]		7	Actinide
Fr	Francium	France	87	&223[223]	1	7	Alkali metal
Ga	Gallium	Latin Gallia (Gaul)	31	&069.723169.723(1)	13	4	Post-transition metal
Gd	Gadolinium	gadolinite	64	&157.253157.25(3)		6	Lanthanide
Ge	Germanium	Germany	32	&072.64172.64(1)	14	4	Metalloid
H	Hydrogen	Greek hydor gennao (liquid-produce)	1	&001.0079471.00794(7)	1	1	Diatomic nonmetal
He	Helium	Greek helios (Sun)	2	&004.00260224.002602(2)	18	1	Noble gas
Hf	Hafnium	Latin Hafnia (Copenhagen)	72	&178.492178.49(2)	4	6	Transition metal
Hg	Mercury	Greek hydrargyrum (liquid silver)	80	&200.592200.59(2)	12	6	Transition metal
Ho	Holmium	Latin Holmia (Stockholm)	67	&164.930322164.930 32(2)		6	Lanthanide
Hs	Hassium	Hesse, Germany	108	&277[277]	8	7	Transition metal
I	Iodine	Greek ioeides (violet)	53	&126.904473126.904 47(3)	17	5	Diatomic nonmetal
In	Indium	indigo blue	49	&114.8183114.818(3)	13	5	Post-transition metal
Ir	Iridium	Greek iris (rainbow)	77	&192.2173192.217(3)	9	6	Transition metal
K	Potassium	Latin kalium (potassium)	19	&039.0983139.0983(1)	1	4	Alkali metal
Kr	Krypton	Greek kryptos (concealment)	36	&083.798283.798(2)	18	4	Noble gas
La	Lanthanum	Greek lanthano (escape)	57	&138.905477138.90547(7)		6	Lanthanide
Li	Lithium	Greek lithos (rock)	3	&006.94126.941(2)	1	2	Alkali metal
Lr	Lawrencium	Ernest O. Lawrence	103	&262[262]	3	7	Actinide
Lu	Lutetium	Latin Lutetia (Paris)	71	&174.9671174.967(1)	3	6	Lanthanide
Lv	Livermorium	Lawrence Livermore National Laboratory	116	&292[292]	16	7	Unknown
Md	Mendelevium	Dmitri Mendeleyev	101	&258[258]		7	Actinide
Mg	Magnesium	Magnesia, Greece	12	&024.3050624.3050(6)	2	3	Alkaline earth metal
Mn	Manganese	Greek magnes (magnet)	25	&054.938045554.938045(5)	7	4	Transition metal
Mo	Molybdenum	Greek molybdos (lead)	42	&095.94295.94(2)	6	5	Transition metal
Mt	Meitnerium	Lise Meitner	109	&268[268]	9	7	Unknown
N	Nitrogen	Greek nitron (niter)	7	&014.0067214.0067(2)	15	2	Diatomic nonmetal
Na	Sodium	Latin natrium (sodium)	11	&022.98976928222.98976928(2)	1	3	Alkali metal
Nb	Niobium	Niobe	41	&092.90638292.906 38(2)	5	5	Transition metal
Nd	Neodymium	Greek neos didymos (novelty-twin)	60	&144.2423144.242(3)		6	Lanthanide
Ne	Neon	Greek neos (novelty)	10	&020.1797620.1797(6)	18	2	Noble gas
Ni	Nickel	German kupfernickel (nickeline)	28	&058.6934258.6934(2)	10	4	Transition metal
No	Nobelium	Alfred Nobel	102	&259[259]		7	Actinide
Np	Neptunium	Neptune	93	&237[237]		7	Actinide
O	Oxygen	Greek oxys (acid)	8	&015.9994315.9994(3)	16	2	Diatomic nonmetal
Os	Osmium	Greek osme (odor)	76	&190.233190.23(3)	8	6	Transition metal
P	Phosphorus	Greek phosphoros (light bearer)	15	&030.973762230.973762(2)	15	3	Polyatomic nonmetal
Pa	Protactinium	Greek protos and actinium	91	&231.035882231.03588(2)		7	Actinide
Pb	Lead	Latin plumbum (lead)	82	&207.21207.2(1)	14	6	Post-transition metal
Pd	Palladium	Pallas (genitive Pallados)	46	&106.421106.42(1)	10	5	Transition metal
Pm	Promethium	Prometheus	61	&145[145]		6	Lanthanide
Po	Polonium	Poland	84	&210[210]	16	6	Post-transition metal
Pr	Praseodymium	Greek prasios (green)	59	&140.907652140.90765(2)		6	Lanthanide
Pt	Platinum	Spanish platina (silver)	78	&195.0849195.084(9)	10	6	Transition metal
Pu	Plutonium	Pluto	94	&244[244]		7	Actinide
Ra	Radium	Latin radius (ray)	88	&226[226]	2	7	Alkaline earth metal
Rb	Rubidium	Latin rubidus (red)	37	&085.4678385.4678(3)	1	5	Alkali metal
Re	Rhenium	German Rheinprovinz	75	&186.2071186.207(1)	7	6	Transition metal
Rf	Rutherfordium	Ernest Rutherford	104	&261261	4	7	Transition metal
Rg	Roentgenium	Wilhelm Conrad Röntgen	111	&272[272]	11	7	Unknown
Rh	Rhodium	Greek rhodon (rose)	45	&102.905502102.905 50(2)	9	5	Transition metal
Rn	Radon	radium and emanation	86	&220[220]	18	6	Noble gas
Ru	Ruthenium	Latin Ruthenia (Russia)	44	&101.072101.07(2)	8	5	Transition metal
S	Sulfur (Sulphur)	Latin sulfur	16	&032.065532.065(5)	16	3	Polyatomic nonmetal
Sb	Antimony	Latin stibium (eye liner)	51	&121.7601121.760(1)	15	5	Metalloid
Sc	Scandium	Scandinavia	21	&044.955912644.955912(6)	3	4	Transition metal
Se	Selenium	Greek selene (Moon)	34	&078.96378.96(3)	16	4	Polyatomic nonmetal
Sg	Seaborgium	Glenn T. Seaborg	106	&266[266]	6	7	Transition metal
Si	Silicon	Latin silex (flint)	14	&028.0855328.0855(3)	14	3	Metalloid
Sm	Samarium	samarskite	62	&150.362150.36(2)		6	Lanthanide
Sn	Tin	Latin stannum (tin)	50	&118.7101118.710(7)	14	5	Post-transition metal
Sr	Strontium	Strontian	38	&087.62187.62(1)	2	5	Alkaline earth metal
Ta	Tantalum	King Tantalus	73	&180.947882180.94788(2)	5	6	Transition metal
Tb	Terbium	Ytterby, Sweden	65	&158.925352158.92535(2)		6	Lanthanide
Tc	Technetium	Greek technetos (artificial)	43	&098[98]	7	5	Transition metal
Te	Tellurium	Greek tellus (Earth)	52	&127.603127.60(3)	16	5	Metalloid
Th	Thorium	Thor	90	&232.038062232.03806(2)		7	Actinide
Ti	Titanium	the Titans	22	&047.867147.867(1)	4	4	Transition metal
Tl	Thallium	Greek thallos (shoot)	81	&204.38332204.3833(2)	13	6	Post-transition metal
Tm	Thulium	Thule and the traditional -ium ending	69	&168.934212168.93421(2)		6	Lanthanide
U	Uranium	Uranus	92	&238.028913238.02891(3)		7	Actinide
Uuo	Ununoctium	Latin uni, uni, and oct (one, one, eight)	118	&294[294]	18	7	Unknown
Uup	Ununpentium	Latin uni, uni, and Greek pent (one, one, five)	115	&288[288]	15	7	Unknown
Uus	Ununseptium	Latin uni, uni, and sept (one, one, seven)	117	&294[294]	17	7	Unknown
Uut	Ununtrium	Latin uni, uni, and Greek tri (one, one, three)	113	&284[284]	13	7	Unknown
V	Vanadium	Vanadis	23	&050.9415150.9415(1)	5	4	Transition metal
W	Tungsten	German wolfram (wolf-froth)	74	&183.841183.84(1)	6	6	Transition metal
Xe	Xenon	Greek xenos (alien)	54	&131.2936131.293(6)	18	5	Noble gas
Y	Yttrium	Ytterby, Sweden	39	&088.90585288.90585(2)	3	5	Transition metal
Yb	Ytterbium	Ytterby, Sweden	70	&173.043173.04(3)		6	Lanthanide
Zn	Zinc	German zin (tin)	30	&065.409465.409(4)	12	4	Transition metal
Zr	Zirconium	zircon	40	&091.224291.224(2)	4	5	Transition metal

Legend for category color

Background color shows subcategory in the metal–metalloid–nonmetal trend: Metal Metalloid Nonmetal Unknown chemical properties Alkali metal Alkaline earth metal Lan­thanide Actinide Transition metal Post-​transition metal Polyatomic nonmetal Diatomic nonmetal Noble gas

Antimatter atoms are denoted by a bar above the symbol for their matter counterpart, so e.g. H is the symbol for antihydrogen.

Symbols not currently used

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

Chemical symbol	Name	Atomic number	Origin of symbol	Why not used
A	Argon	18	Current symbol is Ar.
Ab	Alabamine	85	Discredited claim to discovery of astatine.
Ad	Aldebaranium	70	Former name of ytterbium.
Am	Alabamium	85	Discredited claim to discovery of astatine. The symbol is now used for americium
An	Athenium	99	Proposed name for einsteinium.
Ao	Ausonium	93	Discredited claim to discovery of neptunium.
Az	Azote	7	Former name for nitrogen.
Bo	Boron	5	Current symbol is B.
Bv	Brevium	91	Former name for protactinium.
Bz	Berzelium	59	Suggested name for praseodymium.
Cb	Columbium	41	Former name of niobium.
Cb	Columbium	95	Suggested name for americium.
Ch	Chromium	24	Current symbol is Cr.
Cl	Columbium	41	Former name of niobium. The symbol is now used for chlorine.
Cp	Cassiopeium	71	Former name for lutetium.
Cp	Copernicium	112	Current symbol is Cn.
Ct	Centurium	100	Proposed name for fermium.
Ct	Celtium	72	Former name of hafnium.
Da	Danubium	43	Suggested name for technetium.
Db	Dubnium	104	Proposed name for rutherfordium. The symbol and name were used for element 105.
Di	Didymium		Mixture of the elements praseodymium and neodymium. Mosander wrongly believed didymium to be an element
E	Einsteinium	99	Current symbol is Es.
Ea	Ekaaluminium	31	Name given by Mendeleev to an as of then undiscovered element. When discovered, gallium closely matched the prediction.
Eb	Ekaboron	21	Name given by Mendeleev to an as of then undiscovered element. When discovered, scandium closely matched the prediction.
El	Ekaaluminium	31	Name given by Mendeleev to an as of then undiscovered element. When discovered, gallium closely matched the prediction.
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).
Em	Ekamanganese	43	Name given by Mendeleev to an as of then undiscovered element. When discovered, technetium closely matched the prediction.
Es	Ekasilicon	32	Name given by Mendeleev to an as of then undiscovered element. When discovered, germanium closely matched the prediction. The symbol is now used for einsteinium.
Es	Esperium	94	Discredited claim to discovery of plutonium. The symbol is now used for einsteinium.
Fa	Francium	87	Current symbol is Fr.
Fl	Fluorine	9	Current symbol is F. The symbol are now used for flerovium.
Fl	Florentium	61	Discredited claim to discovery of promethium. The symbol is now used for flerovium.
Fr	Florentium	61	Discredited claim to discovery of promethium. The symbol is now used for francium.
G	Glucinium	4	Former name of beryllium.
Gl	Glucinium	4	Former name of beryllium.
Ha	Hahnium	105	Proposed name for dubnium.
Hn	Hahnium	108	Proposed name for hassium.
Hy	Mercury	80	Current symbol is Hg.
I	Iridium	77	Current symbol is Ir. The symbol is now used for iodine.
Il	Illinium	61	Discredited claim to discovery of promethium.
J	Jodium	53	Old name of iodine.
Jg	Jargonium	72	Discredited claim to discovery of hafnium.
Jl	Joliotium	105	Proposed name for dubnium.
Ku	Kurchatovium	104	Proposed name for rutherfordium.
Lw	Lawrencium	103	Current symbol is Lr.
M	Muriaticum	17	Former name of chlorine.
Ma	Manganese	25	Current symbol is Mn.
Ma	Masurium	43	Disputed claim to discovery of technetium.
Md	Mendelevium	97	Proposed name for berkelium. The symbol and name were later used for element 101.
Me	Mendelevium	68	Suggested name for erbium.
Ml	Moldavium	87	Suggested name for francium.
Ms	Magnesium	12	Current symbol is Mg.
Ms	Masrium	49	Discredited claim of discovery of indium.
Mt	Meitnium	91	Suggested name for protactinium. The symbol is now used for meitnerium.
Mv	Mendelevium	101	Current symbol is Md.
Ng	Norwegium	72	Discredited claim to discovery of hafnium.
No	Norium	72	Discredited claim to discovery of hafnium. The symbol is now used for nobelium.
Ns	Nielsbohrium	105	Proposed name for dubnium.
Ns	Nielsbohrium	107	Proposed name for bohrium.
Nt	Niton	86	Former name for radon.
Ny	Neoytterbium	70	Former name of ytterbium.
Od	Odinium	62	Suggested name for samarium.
P	Lead	82	Current symbol is Pb. The symbol is now used for phosphorus.
Pa	Palladium	46	Current symbol is Pd. The symbol is now used for protactinium.
Pe	Pelopium	41	Former name for niobium.
Pl	Palladium	46	Current symbol is Pd.
Po	Potassium	19	Current symbol is K. The letters were later used for polonium.
R	Rhodium	45	Current symbol is Rh.
Rf	Rutherfordium	106	Proposed name for seaborgium. The symbol and name were instead used for element 104.
Ro	Rhodium	45	Current symbol is Rh.
Sa	Samarium	62	Current symbol is Sm.
So	Sodium	11	Current symbol is Na.
Sp	Spectrium	70	Suggested name for ytterbium.
St	Tin	50	Current symbol is Sn.
St	Antimony	51	Current symbol is Sb.
Tn	Tungsten	74	Current symbol is W.
Tu	Thulium	69	Current symbol is Tm.
Tu	Tungsten	74	Current symbol is W.
Ty	Tyrium	60	Suggested name for neodymium.
Unb	Unnilbium	102	Temporary name given to nobelium until it was permanently named by IUPAC.
Une	Unnilennium	109	Temporary name given to meitnerium until it was permanently named by IUPAC.
Unh	Unnilhexium	106	Temporary name given to seaborgium until it was permanently named by IUPAC.
Uno	Unniloctium	108	Temporary name given to hassium until it was permanently named by IUPAC.
Unp	Unnilpentium	105	Temporary name given to dubnium until it was permanently named by IUPAC.
Unq	Unnilquadium	104	Temporary name given to rutherfordium until it was permanently named by IUPAC.
Uns	Unnilseptium	107	Temporary name given to bohrium until it was permanently named by IUPAC.
Unt	Unniltrium	103	Temporary name given to lawrencium until it was permanently named by IUPAC.
Unu	Unnilunium	101	Temporary name given to mendelevium until it was permanently named by IUPAC.
Uub	Ununbium	112	Temporary name given to copernicium until it was permanently named by IUPAC.
Uuh	Ununhexium	116	Temporary name given to livermorium until it was permanently named by IUPAC.
Uun	Ununnilium	110	Temporary name given to darmstadtium until it was permanently named by IUPAC.
Uuq	Ununquadium	114	Temporary name given to flerovium until it was permanently named by IUPAC.
Uuu	Unununium	111	Temporary name given to roentgenium until it was permanently named by IUPAC.
Ur	Uranium	92	Current symbol is U.
Vi	Virginium	87	Discredited claim to discovery of francium.
Vm	Virginium	87	Discredited claim to discovery of francium.
Yt	Yttrium	39	Current symbol is Y.

Pictographic symbols

The following is a list of pictographic symbols employed to symbolize elements known since ancient times (for example to the alchemists). Not included in this list are symbolic representations of substances previously called elements (such as certain rare earth mineral blends and the classical elements fire and water of ancient philosophy) which are known today to be multi-atomic. Also not included are symbolic representations currently used for elements in other languages such as the Chinese characters for elements. Modern alphabetic notation was introduced in 1814 by Jöns Jakob Berzelius.

Chemical symbol	Original name	Modern name	Atomic number	Origin of symbol
	Hydrogen	Hydrogen	1	Daltonian symbol circa 1808.
	Sulfur	Sulfur	16	Alchemical symbol.
	Pallas	Sulfur	16	Alchemical symbol.
🜍	Sulfur	Sulfur	16	Alchemical symbol.
♁	Sulfur	Sulfur	16	Daltonian symbol circa 1808.
⊛	Magnesium	Magnesium	12	Alchemical symbol.
♂	Mars	Iron	26	Alchemical symbol.
	Stellae Fixae	Copper	29	Pre–16th-century alchemical symbol.
♀	Venus	Copper	29	Alchemical symbol.
	Copper	Copper	29	Alchemical symbol.
©	Copper	Copper	29	Daltonian symbol circa 1808.
	Arsenic	Arsenic	33	Alchemical symbol.
🜺	Arsenic	Arsenic	33	Alchemical symbol.
☽	Luna	Silver	47	Alchemical symbol.
🜛	Silver	Silver	47	Alchemical symbol.
♃	Iupiter	Tin	50	Alchemical symbol.
♁	Antimony	Antimony	51	Alchemical symbol.
	Antimony	Antimony	51	Alchemical symbol.
☾	Platinum	Platinum	78	Alchemical symbol.
☉	Platinum	Platinum	78	Alchemical symbol.
	Uranus	Platinum	78	Alchemical symbol.
☼	Sol	Gold	79	Alchemical symbol from the 16th century.
	Sol	Gold	79	Alchemical symbol from 1700 through 1783.
🜚	Gold	Gold	79	Alchemical symbol.
	Pisces	Mercury	80	Pre–16th-century alchemical symbol.
	Neptunus	Mercury	80	Alchemical symbol from the 17th century.
☿	Mercurius	Mercury	80	Alchemical symbol from 1700 through 1783.
♄	Saturnus	Lead	82	Alchemical symbol circa 1783.
	Taurus	Bismuth	83	Alchemical symbol.

Symbols for named isotopes

The following is a list of isotopes of elements given in the previous tables which have been designated unique symbols. By this it is meant that a comprehensive list of current systematic symbols (in the ^uAtom form) are not included in the list and can instead be found in the Isotope index chart. The symbols for the named isotopes of hydrogen, deuterium (D) and tritium (T) are still in use today. 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 and C₆D₆ can be used instead of [²H₆]C₆H₆.

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

Chemical symbol	Name	Atomic number	Origin of symbol
Ac	Actinium	89	From the 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 at one time 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 at one time 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 234Pa, 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

General:

• E: any element
• M: metal – any metal atom
• Mu: muonium
• Ps: positronium
• St: steel (occasionally used)
• X: halogen – any halogen atom

From organic chemistry:

• Ac: acetyl – (also used for the element actinium: see above)
• Ad: adamantyl
• Ak: alkyl
• Ar: aryl – (also used for the element argon: see above)
• Bn: benzyl
• Bu: butyl
• Bz: benzoyl – (also used for berzelium, an old suggested name for praseodymium).
• Cp: cyclopentadienyl
• Cy: cyclohexyl
• Et: ethyl
• i-Pr: isopropyl
• Me: methyl
• Mes: mesityl (2,3,6-trimethylphenyl)
• Ms: mesyl (methylsulfonyl)
• Np: neopentyl - (also used for the element neptunium: see above)
• Ph: phenyl
• Pr: propyl – (also used for the element praseodymium: see above)
• R: radical – some unspecified element or radical
• t-Bu: tert-butyl
• Tf: triflyl (trifluoromethanesulfonyl)
• Tr: trityl (triphenylmethyl)
• Ts: tosyl

From inorganic chemistry:

• Ab: albite
• Di: didymium – rare earth metal that proved to be a mixture of the elements praseodymium and neodymium.
• Dp: decipium – rare earth metal that proved to be a mixture of the elements samarium, neodymium and praseodymium.
• Pp: philippium – rare earth metal that proved to be a mixture of the elements holmium and samarium.

See also

• List of chemical elements naming controversies
• List of elements
• Nuclear notation

References

• Element name etymologies. Retrieved July 15, 2005.
• Atomic Weights of the Elements 2001, Pure Appl. Chem. 75(8), 1107–1122, 2003. Retrieved June 30, 2005. Atomic weights of elements with atomic numbers from 1–109 taken from this source.
• IUPAC Standard Atomic Weights Revised (2005).
• WebElements Periodic Table. Retrieved June 30, 2005. Atomic weights of elements with atomic numbers 110–116 taken from this source.
• Lapp, Ralph E. Matter. Life Science Library. New York: Time, Inc. 1963.
• Leighton, Robert B. Principles of Modern Physics. New York: McGraw-Hill. 1959.
• Scerri, E.R. "The Periodic Table, Its Story and Its Significance". New York, Oxford University Press. 2007.

External links

• Berzelius' List of Elements
• History of IUPAC Atomic Weight Values (1883 to 1997)
• American Chemical Society, Committee on Nomenclature, Terminology & Symbols