Chemical symbol

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

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 ; Hg is the symbol for mercury ; and He is the symbol for helium because helium was not known in ancient Roman times. Some symbols come from other sources, like W for tungsten which was not known in Roman times.
A three-letter temporary symbol may be assigned to a newly synthesized element. For example, "Uno" was the temporary symbol for hassium 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

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. 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 is shown in the left superscript position. This number defines the specific isotope. Various letters, such as "m" and "f" may also be used here to indicate a nuclear isomer. Alternately, the number here can represent a specific spin state. These details can be omitted if not relevant in a certain context.
The proton number may be indicated in the left subscript position. 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.
The number of atoms of an element in a molecule or chemical compound is shown in the right subscript position. 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. 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

Symbols and names not currently used

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.
Ab	Alabamine	85	Discredited claim to discovery of astatine.
Ad	Aldebaranium	70	Former name for ytterbium.
Ah	Anglohelvetium	85	Discredited claim to discovery of astatine.
Ak	Alkalinium	87	Discredited claim to discovery of francium.
Am	Alabamine	85	Discredited claim to discovery of astatine. The symbol Am is now used for americium.
An	Athenium	99	Proposed name for einsteinium.
Ao	Ausonium	93	Discredited claim to discovery of neptunium.
At	Austriacum	84	Discredited claim to discovery of polonium. The symbol At is now used for astatine.
Az	Azote	7	Former name for nitrogen.
Bo	Bohemium	93	Discredited claim to discovery of neptunium.
Bo	Boron	5	Current symbol is B.
Bv	Brevium	91	Former name for protactinium-234.
Bz	Berzelium	90	Baskerville wrongly believed berzelium was a new element. Was actually thorium.
Cb	Columbium	41	Former name for niobium.
Ch	Chromium	24	Current symbol is Cr.
Cl	Columbium	41	Former name for niobium. The symbol Cl is now used for chlorine.
Cm	Catium	87	Proposed name for francium. The symbol Cm is now used for curium.
Cn	Carolinium	90	Baskerville wrongly believed carolinium to be a new element. Was actually thorium. The symbol Cn is now used for copernicium.
Cp	Cassiopeium	71	Former name for lutetium.
Cp	Copernicium	112	Current symbol is Cn.
Ct	Celtium	72	Discredited claim to discovery of hafnium.
Ct	Centurium	100	Proposed name for fermium.
Cy	Cyclonium	61	Proposed name for promethium.
D	Didymium	59/60	Mixture of the elements praseodymium and neodymium. Mosander wrongly believed didymium to be an element.
Da	Davyum	43	Discredited claim to discovery of technetium.
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.
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.
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.
Do	Dor	85	Discredited claim to discovery of astatine made by Horia Hulubei and Yvette Cauchois.
Dn	Dubnadium	118	Proposed name for oganesson.
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.
Dt	Dvitellurium	84	Name given by Mendeleev to an as of then undiscovered element. When discovered, polonium closely matched the prediction.
E	Einsteinium	99	Current symbol is Es.
E	Erbium	68	Current symbol is Er.
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.
Eb	Erebodium	42	Alexander Pringle wrongly believed erebodium to be a new element. Was likely molybdenum.
El	Ekaaluminium	31	Name given by Mendeleev to an as of then undiscovered element. When discovered, gallium closely matched the prediction.
Em	Ekamanganese	43	Name given by Mendeleev to an as of then undiscovered element. When discovered, technetium 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.
Em	Emanium	89	Alternate name formerly proposed for actinium.
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.
Hs	Hesperium	94	Discredited claim to discovery of plutonium. The symbol Hs is now used for hassium.
Et	Ekatantalum	91	Name given by Mendeleev to an as of then undiscovered element. When discovered, protactinium closely matched the prediction.
Ex	Euxenium	72	Discredited claim to discovery of hafnium.
Fa	Francium	87	Current symbol is Fr.
Fl	Florentium	61	Discredited claim to discovery of promethium. The symbol Fl is now used for flerovium.
Fl	Fluorine	9	Current symbol is F. The symbol Fl is now used for flerovium.
Fr	Florentium	61	Discredited claim to discovery of promethium. The symbol Fr is now used for francium.
G	Glucinium	4	Former name for beryllium.
Gh	Ghiorsium	118	Discredited claim to discovery of oganesson.
Gl	Glucinium	4	Former name for beryllium.
Ha	Hahnium	105	Proposed name for dubnium.
Hn	Hahnium	108	Proposed name for hassium.
Hv	Helvetium	85	Discredited claim to discovery of astatine.
Hy	Mercury	80	Hy from the Greek hydrargyrum for "liquid silver". Current symbol is Hg.
I	Iridium	77	Current symbol is Ir. The symbol I is now used for iodine.
Ic	Incognitium	65	Demarçay wrongly believed incognitium to be a new element. Was actually terbium mixed with gadolinium.
Il	Illinium	61	Discredited claim to discovery of promethium.
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.
Jg	Jargonium	72	Discredited claim to discovery of hafnium.
Jl	Joliotium	105	Proposed name for dubnium.
Jp	Japonium	113	Proposed name for nihonium.
Ka	Potassium	19	Current symbol is K.
Ku	Kurchatovium	104	Proposed name for rutherfordium.
L	Lithium	3	Current symbol is Li.
Lw	Lawrencium	103	Current symbol is Lr.
M	Muriaticum	17	Former name for 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.
Ml	Moldavium	87	Discredited claim to discovery of francium made by Horia Hulubei and Yvette Cauchois.
Ms	Magnesium	12	Current symbol is Mg.
Ms	Masrium	88	Discredited claim to discovery of radium.
Ms	Masurium	43	Disputed claim to discovery of technetium.
Ms	Mosandrium	65	Smith wrongly believed mosandrium to be a new element. Was actually terbium.
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 No is now used for nobelium.
Np	Neptunium	91	Discredited claim to discovery of protactinium. The symbol and name were later used for element 93.
Np	Nipponium	43	Discredited claim to discovery of technetium. The symbol Np is now used for neptunium.
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 for ytterbium.
P	Lead	82	Current symbol is Pb. The symbol P is now used for phosphorus.
Pa	Palladium	46	Current symbol is Pd. The symbol Pa is now used for protactinium.
Pe	Pelopium	41	Former name for niobium.
Ph	Phosphorus	15	Current symbol is P.
Pl	Palladium	46	Current symbol is Pd.
Pm	Polymnestum	33	Alexander Pringle wrongly believed polymnestum to be a new element. Was likely arsenic. The symbol Pm is now used for promethium.
Po	Potassium	19	Current symbol is K. The symbol Po is now used for polonium.
Pp	Philippium	67	Delafontaine discovered a new element and named it philippium. Per Teodor Cleve isolated it and renamed it holmium.
R	Rhodium	45	Current symbol is Rh.
Rd	Radium	88	Current symbol is Ra.
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.
Sq	Sequanium	93	Discredited claim to discovery of neptunium made by Horia Hulubei and Yvette Cauchois.
St	Antimony	51	Current symbol is Sb.
St	Tin	50	Current symbol is Sn.
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.
Tn	Tungsten	74	Current symbol is W.
Tr	Terbium	65	Current symbol is Tb.
Tu	Thulium	69	Current symbol is Tm.
Tu	Tungsten	74	Current symbol is W.
Ur	Uralium	75	Discredited claim to discovery of rhenium.
Ur	Uranium	92	Current symbol is U.
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.
Vm	Virginium	87	Discredited claim to discovery of francium.
Va	Vanadium	23	Current symbol is V.
Wo	Wolfram	74	Former name for tungsten.
X	Xenon	54	Current symbol is Xe. The symbol X is now used for any halogen.
Yt	Yttrium	39	Current symbol is Y.