Chemical symbol

Chemical symbols are abbreviations used in chemistry for chemical elements, functional groups and chemical compounds. Element symbols for chemical elements normally consist of one or two letters from the Latin alphabet and are written with the first letter capitalised.

Earlier symbols for chemical elements stem from classical Latin and Greek vocabulary. 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 new 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 3-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 its atomic number being 8 greater than 100. There are also some historical symbols that are no longer officially used.

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.

Annotated example of an atomic 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.

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.

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

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.

Hazard pictographs are another type of symbols used in chemistry.

Symbols for chemical elements

List of chemical elements
Z[upper-roman 1]	Symbol	Element	Origin of name[2][3]	Group	Period	Atomic weight[4][5] (u (±))

1	H	Hydrogen	Greek elements hydro- and -gen, meaning 'water-forming'	1	1	1.008[upper-roman 2][upper-roman 3][upper-roman 4][upper-roman 5]
2	He	Helium	Greek hḗlios, 'sun'	18	1	4.002602(2)[upper-roman 2][upper-roman 4]
3	Li	Lithium	Greek líthos, 'stone'	1	2	6.94[upper-roman 2][upper-roman 3][upper-roman 4][upper-roman 6][upper-roman 5]
4	Be	Beryllium	beryl, a mineral (ultimately from the name of Belur in southern India)	2	2	9.0121831(5)
5	B	Boron	borax, a mineral (from Arabic bawraq)	13	2	10.81[upper-roman 2][upper-roman 3][upper-roman 4][upper-roman 5]
6	C	Carbon	Latin carbo, 'coal'	14	2	12.011[upper-roman 2][upper-roman 4][upper-roman 5]
7	N	Nitrogen	Greek nítron and -gen, meaning 'niter-forming'	15	2	14.007[upper-roman 2][upper-roman 4][upper-roman 5]
8	O	Oxygen	Greek oxy- and -gen, meaning 'acid-forming'	16	2	15.999[upper-roman 2][upper-roman 4][upper-roman 5]
9	F	Fluorine	Latin fluere, 'to flow'	17	2	18.998403163(6)
10	Ne	Neon	Greek néon, 'new'	18	2	20.1797(6)[upper-roman 2][upper-roman 3]
11	Na	Sodium	English soda (the symbol Na is derived from New Latin natrium, coined from German Natron, 'natron')	1	3	22.98976928(2)
12	Mg	Magnesium	Magnesia, a district of Eastern Thessaly in Greece	2	3	24.305[upper-roman 5]
13	Al	Aluminium	alumina, from Latin alumen (gen. aluminis), 'bitter salt, alum'	13	3	26.9815384(3)
14	Si	Silicon	Latin silex, 'flint' (originally silicium)	14	3	28.085[upper-roman 4][upper-roman 5]
15	P	Phosphorus	Greek phōsphóros, 'light-bearing'	15	3	30.973761998(5)
16	S	Sulfur	Latin sulphur, 'brimstone'	16	3	32.06[upper-roman 2][upper-roman 4][upper-roman 5]
17	Cl	Chlorine	Greek chlōrós, 'greenish yellow'	17	3	35.45[upper-roman 2][upper-roman 3][upper-roman 4][upper-roman 5]
18	Ar	Argon	Greek argós, 'idle' (because of its inertness)	18	3	39.948[upper-roman 2][upper-roman 4][upper-roman 5]
19	K	Potassium	New Latin potassa, 'potash' (the symbol K is derived from Latin kalium)	1	4	39.0983(1)
20	Ca	Calcium	Latin calx, 'lime'	2	4	40.078(4)[upper-roman 2]
21	Sc	Scandium	Latin Scandia, 'Scandinavia'	3	4	44.955908(5)
22	Ti	Titanium	Titans, the sons of the Earth goddess of Greek mythology	4	4	47.867(1)
23	V	Vanadium	Vanadis, an Old Norse name for the Scandinavian goddess Freyja	5	4	50.9415(1)
24	Cr	Chromium	Greek chróma, 'colour'	6	4	51.9961(6)
25	Mn	Manganese	corrupted from magnesia negra; see Magnesium	7	4	54.938043(2)
26	Fe	Iron	English word (the symbol Fe is derived from Latin ferrum)	8	4	55.845(2)
27	Co	Cobalt	German Kobold, 'goblin'	9	4	58.933194(3)
28	Ni	Nickel	Nickel, a mischievous sprite of German miner mythology	10	4	58.6934(4)
29	Cu	Copper	English word, from Latin cuprum, from Ancient Greek Kýpros 'Cyprus'	11	4	63.546(3)[upper-roman 4]
30	Zn	Zinc	Most likely from German Zinke, 'prong' or 'tooth', though some suggest Persian sang, 'stone'	12	4	65.38(2)
31	Ga	Gallium	Latin Gallia, 'France'	13	4	69.723(1)
32	Ge	Germanium	Latin Germania, 'Germany'	14	4	72.630(8)
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'	15	4	74.921595(6)
34	Se	Selenium	Greek selḗnē, 'moon'	16	4	78.971(8)[upper-roman 4]
35	Br	Bromine	Greek brômos, 'stench'	17	4	79.904[upper-roman 5]
36	Kr	Krypton	Greek kryptós, 'hidden'	18	4	83.798(2)[upper-roman 2][upper-roman 3]
37	Rb	Rubidium	Latin rubidus, 'deep red'	1	5	85.4678(3)[upper-roman 2]
38	Sr	Strontium	Strontian, a village in Scotland	2	5	87.62(1)[upper-roman 2][upper-roman 4]
39	Y	Yttrium	Ytterby, a village in Sweden	3	5	88.90584(1)
40	Zr	Zirconium	zircon, a mineral	4	5	91.224(2)[upper-roman 2]
41	Nb	Niobium	Niobe, daughter of king Tantalus from Greek mythology	5	5	92.90637(1)
42	Mo	Molybdenum	Greek molýbdaina, 'piece of lead', from mólybdos, 'lead'	6	5	95.95(1)[upper-roman 2]
43	Tc	Technetium	Greek tekhnētós, 'artificial'	7	5	[98][upper-roman 7]
44	Ru	Ruthenium	New Latin Ruthenia, 'Russia'	8	5	101.07(2)[upper-roman 2]
45	Rh	Rhodium	Greek rhodóeis, 'rose-coloured', from rhódon, 'rose'	9	5	102.90549(2)
46	Pd	Palladium	the asteroid Pallas, considered a planet at the time	10	5	106.42(1)[upper-roman 2]
47	Ag	Silver	English word (The symbol derives from Latin argentum)	11	5	107.8682(2)[upper-roman 2]
48	Cd	Cadmium	New Latin cadmia, from King Kadmos	12	5	112.414(4)[upper-roman 2]
49	In	Indium	Latin indicum, 'indigo' (colour found in its spectrum)	13	5	114.818(1)
50	Sn	Tin	English word (The symbol derives from Latin stannum)	14	5	118.710(7)[upper-roman 2]
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'.)	15	5	121.760(1)[upper-roman 2]
52	Te	Tellurium	Latin tellus, 'the ground, earth'	16	5	127.60(3)[upper-roman 2]
53	I	Iodine	French iode, from Greek ioeidḗs, 'violet'	17	5	126.90447(3)
54	Xe	Xenon	Greek xénon, neuter form of xénos 'strange'	18	5	131.293(6)[upper-roman 2][upper-roman 3]
55	Cs	Caesium	Latin caesius, 'sky-blue'	1	6	132.90545196(6)
56	Ba	Barium	Greek barýs, 'heavy'	2	6	137.327(7)
57	La	Lanthanum	Greek lanthánein, 'to lie hidden'	3	6	138.90547(7)[upper-roman 2]
58	Ce	Cerium	the dwarf planet Ceres, considered a planet at the time		6	140.116(1)[upper-roman 2]
59	Pr	Praseodymium	Greek prásios dídymos, 'green twin'		6	140.90766(1)
60	Nd	Neodymium	Greek néos dídymos, 'new twin'		6	144.242(3)[upper-roman 2]
61	Pm	Promethium	Prometheus of Greek mythology		6	[145][upper-roman 7]
62	Sm	Samarium	samarskite, a mineral named after Colonel Vasili Samarsky-Bykhovets, Russian mine official		6	150.36(2)[upper-roman 2]
63	Eu	Europium	Europe		6	151.964(1)[upper-roman 2]
64	Gd	Gadolinium	gadolinite, a mineral named after Johan Gadolin, Finnish chemist, physicist and mineralogist		6	157.25(3)[upper-roman 2]
65	Tb	Terbium	Ytterby, a village in Sweden		6	158.925354(8)
66	Dy	Dysprosium	Greek dysprósitos, 'hard to get'		6	162.500(1)[upper-roman 2]
67	Ho	Holmium	New Latin Holmia, 'Stockholm'		6	164.930328(7)
68	Er	Erbium	Ytterby, a village in Sweden		6	167.259(3)[upper-roman 2]
69	Tm	Thulium	Thule, the ancient name for an unclear northern location		6	168.934218(6)
70	Yb	Ytterbium	Ytterby, a village in Sweden		6	173.045(10)[upper-roman 2]
71	Lu	Lutetium	Latin Lutetia, 'Paris'		6	174.9668(1)[upper-roman 2]
72	Hf	Hafnium	New Latin Hafnia, 'Copenhagen' (from Danish havn)	4	6	178.49(2)
73	Ta	Tantalum	King Tantalus, father of Niobe from Greek mythology	5	6	180.94788(2)
74	W	Tungsten	Swedish tung sten, 'heavy stone' (The symbol is from wolfram, the old name of the tungsten mineral wolframite)	6	6	183.84(1)
75	Re	Rhenium	Latin Rhenus, 'the Rhine'	7	6	186.207(1)
76	Os	Osmium	Greek osmḗ, 'smell'	8	6	190.23(3)[upper-roman 2]
77	Ir	Iridium	Iris, the Greek goddess of the rainbow	9	6	192.217(2)
78	Pt	Platinum	Spanish platina, 'little silver', from plata 'silver'	10	6	195.084(9)
79	Au	Gold	English word (The symbol derives from Latin aurum)	11	6	196.966570(4)
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')	12	6	200.592(3)
81	Tl	Thallium	Greek thallós, 'green shoot or twig'	13	6	204.38[upper-roman 5]
82	Pb	Lead	English word (The symbol derives from Latin plumbum)	14	6	207.2(1)[upper-roman 2][upper-roman 4]
83	Bi	Bismuth	German Wismut, from weiß Masse 'white mass', unless from Arabic	15	6	208.98040(1)[upper-roman 7]
84	Po	Polonium	Latin Polonia, 'Poland' (the home country of Marie Curie)	16	6	[209][upper-roman 7]
85	At	Astatine	Greek ástatos, 'unstable'	17	6	[210][upper-roman 7]
86	Rn	Radon	radium	18	6	[222][upper-roman 7]
87	Fr	Francium	France	1	7	[223][upper-roman 7]
88	Ra	Radium	French radium, from Latin radius, 'ray'	2	7	[226][upper-roman 7]
89	Ac	Actinium	Greek aktís, 'ray'	3	7	[227][upper-roman 7]
90	Th	Thorium	Thor, the Scandinavian god of thunder		7	232.0377(4)[upper-roman 7][upper-roman 2]
91	Pa	Protactinium	proto- (from Greek prôtos, 'first, before') + actinium, which is produced through the radioactive decay of protactinium		7	231.03588(1)[upper-roman 7]
92	U	Uranium	Uranus, the seventh planet in the Solar System		7	238.02891(3)[upper-roman 7]
93	Np	Neptunium	Neptune, the eighth planet in the Solar System		7	[237][upper-roman 7]
94	Pu	Plutonium	the dwarf planet Pluto, considered the ninth planet in the Solar System at the time		7	[244][upper-roman 7]
95	Am	Americium	The Americas, as the element was first synthesised on the continent, by analogy with europium		7	[243][upper-roman 7]
96	Cm	Curium	Pierre Curie and Marie Curie, French physicists and chemists		7	[247][upper-roman 7]
97	Bk	Berkelium	Berkeley, California, where the element was first synthesised, by analogy with terbium		7	[247][upper-roman 7]
98	Cf	Californium	California, where the element was first synthesised		7	[251][upper-roman 7]
99	Es	Einsteinium	Albert Einstein, German physicist		7	[252][upper-roman 7]
100	Fm	Fermium	Enrico Fermi, Italian physicist		7	[257][upper-roman 7]
101	Md	Mendelevium	Dmitri Mendeleev, Russian chemist and inventor who proposed the periodic table		7	[258][upper-roman 7]
102	No	Nobelium	Alfred Nobel, Swedish chemist and engineer		7	[259][upper-roman 7]
103	Lr	Lawrencium	Ernest O. Lawrence, American physicist		7	[266][upper-roman 7]
104	Rf	Rutherfordium	Ernest Rutherford, British chemist and physicist	4	7	[267][upper-roman 7]
105	Db	Dubnium	Dubna, Russia, where the Joint Institute for Nuclear Research is located	5	7	[268][upper-roman 7]
106	Sg	Seaborgium	Glenn T. Seaborg, American chemist	6	7	[269][upper-roman 7]
107	Bh	Bohrium	Niels Bohr, Danish physicist	7	7	[270][upper-roman 7]
108	Hs	Hassium	New Latin Hassia, 'Hesse' (a state in Germany)	8	7	[270][upper-roman 7]
109	Mt	Meitnerium	Lise Meitner, Austrian physicist	9	7	[278][upper-roman 7]
110	Ds	Darmstadtium	Darmstadt, Germany, where the element was first synthesised	10	7	[281][upper-roman 7]
111	Rg	Roentgenium	Wilhelm Conrad Röntgen, German physicist	11	7	[282][upper-roman 7]
112	Cn	Copernicium	Nicolaus Copernicus, Polish astronomer	12	7	[285][upper-roman 7]
113	Nh	Nihonium	Japanese Nihon, 'Japan' (where the element was first synthesised)	13	7	[286][upper-roman 7]
114	Fl	Flerovium	Flerov Laboratory of Nuclear Reactions, part of JINR, where the element was synthesised; itself named after Georgy Flyorov, Russian physicist	14	7	[289][upper-roman 7]
115	Mc	Moscovium	Moscow Oblast, Russia, where the element was first synthesised	15	7	[290][upper-roman 7]
116	Lv	Livermorium	Lawrence Livermore National Laboratory in Livermore, California, which collaborated with JINR on its synthesis	16	7	[293][upper-roman 7]
117	Ts	Tennessine	Tennessee, United States	17	7	[294][upper-roman 7]
118	Og	Oganesson	Yuri Oganessian, Russian physicist	18	7	[294][upper-roman 7]
Notes Z is the standard symbol for atomic number The isotopic composition of this element varies in some geological specimens, and the variation may exceed the uncertainty stated in the table. The isotopic composition of the element can vary in commercial materials, which can cause the atomic weight to deviate significantly from the given value. The isotopic composition varies in terrestrial material such that a more precise atomic weight can not be given. The value listed is the conventional atomic-weight value suitable for trade and commerce. The actual value may differ depending on the isotopic composition of the sample. Since 2009, IUPAC provides the standard atomic-weight values for these elements using the interval notation. The corresponding standard atomic weights are: Hydrogen: [1.00784, 1.00811] Lithium: [6.938, 6.997] Boron: [10.806, 10.821] Carbon: [12.0096, 12.0116] Nitrogen: [14.00643, 14.00728] Oxygen: [15.99903, 15.99977] Magnesium: [24.304, 24.307] Silicon: [28.084, 28.086] Sulfur: [32.059, 32.076] Chlorine: [35.446, 35.457] Argon: [39.792, 39.963] Bromine: [79.901, 79.907] Thallium: [204.382, 204.385] The atomic weight of commercial lithium can vary between 6.939 and 6.996—analysis of the specific material is necessary to find a more accurate value. The element does not have any stable nuclides, and a value in brackets, e.g. [209], indicates the mass number of the longest-lived isotope of the element. However, four such elements, bismuth, thorium, protactinium, and uranium, have characteristic terrestrial isotopic compositions, and thus their standard atomic weights are given.

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

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.

Chemical symbol	Name	Atomic number	Origin of symbol	Why not used	Refs
A	Argon	18	A used for Argon until 1957. Current symbol is Ar.	[nb 1]	[6]
Ab	Alabamine	85	Discredited claim to discovery of astatine.	[nb 2]	[7][8]
Ad	Aldebaranium	70	Former name for ytterbium.	[nb 2]
Am	Alabamine	85	Discredited claim to discovery of astatine. The symbol is now used for americium.	[nb 2]	[7][8]
An	Athenium	99	Proposed name for einsteinium.	[nb 3]
Ao	Ausonium	93	Discredited claim to discovery of neptunium.	[nb 2]	[7]
Az	Azote	7	Former name for nitrogen.	[nb 1]
Bo	Boron	5	Current symbol is B.	[nb 1]
Bv	Brevium	91	Former name for protactinium.	[nb 1]
Bz	Berzelium	90	Baskerville wrongly believed berzelium to be a new element. Was actually thorium.	[nb 3]	[9]
Cb	Columbium	41	Former name for niobium.	[nb 1]	[7][9]
Ch	Chromium	24	Current symbol is Cr.	[nb 1]
Cl	Columbium	41	Former name for niobium. The symbol is now used for chlorine.	[nb 1]
Cn	Carolinium	90	Baskerville wrongly believed carolinium to be a new element. Was actually thorium. The symbol is now used for copernicium.		[9]
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]
D	Didymium	59/60	Mixture of the elements praseodymium and neodymium. Mosander wrongly believed didymium to be an element.		[10]
Da	Davyum	43	Discredited claim to discovery of technetium.	[nb 2]	[7]
Db	Dubnium	104	Proposed name for rutherfordium. The symbol and name were instead used for element 105.	[nb 1][nb 3]	[7]
Di	Didymium	59/60	Mixture of the elements praseodymium and neodymium. Mosander wrongly believed didymium to be an element.		[10]
Ds	Dysprosium	66	Current symbol is Dy. The symbol is now used for darmstadtium.	[nb 1]
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]	[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]	[7]
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]	[7]
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]	[7]
Em	Emanium	89	Alternate name formerly proposed for actinium.	[nb 3]
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.	[nb 3][nb 4]	[7]
Es	Esperium	94	Discredited claim to discovery of plutonium. The symbol is now used for einsteinium.	[nb 2]	[7]
Fa	Francium	87	Current symbol is Fr.	[nb 1]
Fl	Florentium	61	Discredited claim to discovery of promethium. The symbol is now used for flerovium.	[nb 2]
Fl	Fluorine	9	Current symbol is F. The symbol is now used for flerovium.	[nb 1]
Fr	Florentium	61	Discredited claim to discovery of promethium. The symbol is now used for francium.	[nb 2]	[7]
G	Glucinium	4	Former name for beryllium.	[nb 1]
Gl	Glucinium	4	Former name for beryllium.	[nb 1]	[7]
Ha	Hahnium	105	Proposed name for dubnium.	[nb 3]
Hn	Hahnium	108	Proposed name for hassium.	[nb 3]	[7]
Hv	Helvetium	85	Discredited claim to discovery of astatine.	[nb 2]	[9]
Hy	Mercury	80	Hy from the Greek hydrargyrum for "liquid silver". Current symbol is Hg.	[nb 1]	[6]
I	Iridium	77	Current symbol is Ir. The symbol is now used for iodine.	[nb 1]
Il	Illinium	61	Discredited claim to discovery of promethium.	[nb 2]	[7]
J	Jodium	53	Former name for iodine.	[nb 1]
Jg	Jargonium	72	Discredited claim to discovery of hafnium.	[nb 2]	[7]
Jl	Joliotium	105	Proposed name for dubnium.	[nb 3]	[7]
Ka	Potassium	19	Current symbol is K.	[nb 1]
Ku	Kurchatovium	104	Proposed name for rutherfordium.	[nb 3]	[7]
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]	[7]
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.	[nb 2]	[9]
Ms	Magnesium	12	Current symbol is Mg.	[nb 1]
Ms	Masurium	43	Disputed claim to discovery of technetium.	[nb 2]
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 is now used for nobelium.	[nb 2]
Np	Nipponium	43	Discredited claim to discovery of technetium. The symbol is now used for neptunium.	[nb 2]	[7]
Ns	Nielsbohrium	105	Proposed name for dubnium.	[nb 3]	[7]
Ns	Nielsbohrium	107	Proposed name for bohrium.	[nb 3]	[7]
Nt	Niton	86	Former name for radon.	[nb 1]	[7]
Ny	Neoytterbium	70	Former name for ytterbium.	[nb 1]
P	Lead	82	Current symbol is Pb. The symbol is now used for phosphorus.	[nb 1]
Pa	Palladium	46	Current symbol is Pd. The symbol is now used for protactinium.	[nb 1]
Pe	Pelopium	41	Former name for niobium.	[nb 1]
Pl	Palladium	46	Current symbol is Pd.	[nb 1]
Po	Potassium	19	Current symbol is K. The symbol is now used for polonium.	[nb 1]
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]	[7]
Ro	Rhodium	45	Current symbol is Rh.	[nb 1]
Sa	Samarium	62	Current symbol is Sm.	[nb 1]	[7]
So	Sodium	11	Current symbol is Na.	[nb 1]
St	Antimony	51	Current symbol is Sb.	[nb 1]
St	Tin	50	Current symbol is Sn.	[nb 1]
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]
Unb	Unnilbium	102	Temporary name given to nobelium until it was permanently named by IUPAC.	[nb 4]
Une	Unnilennium	109	Temporary name given to meitnerium until it was permanently named by IUPAC.	[nb 4]
Unh	Unnilhexium	106	Temporary name given to seaborgium until it was permanently named by IUPAC.	[nb 4]
Uno	Unniloctium	108	Temporary name given to hassium until it was permanently named by IUPAC.	[nb 4]
Unp	Unnilpentium	105	Temporary name given to dubnium until it was permanently named by IUPAC.	[nb 4]
Unq	Unnilquadium	104	Temporary name given to rutherfordium until it was permanently named by IUPAC.	[nb 4]
Uns	Unnilseptium	107	Temporary name given to bohrium until it was permanently named by IUPAC.	[nb 4]
Unt	Unniltrium	103	Temporary name given to lawrencium until it was permanently named by IUPAC.	[nb 4]
Unu	Unnilunium	101	Temporary name given to mendelevium until it was permanently named by IUPAC.	[nb 4]
Uub	Ununbium	112	Temporary name given to copernicium until it was permanently named by IUPAC.	[nb 4]
Uuh	Ununhexium	116	Temporary name given to livermorium until it was permanently named by IUPAC.	[nb 4]
Uun	Ununnilium	110	Temporary name given to darmstadtium until it was permanently named by IUPAC.	[nb 4]
Uuo	Ununoctium	118	Temporary name given to oganesson until it was permanently named by IUPAC.	[nb 4]
Uup	Ununpentium	115	Temporary name given to moscovium until it was permanently named by IUPAC.	[nb 4]
Uuq	Ununquadium	114	Temporary name given to flerovium until it was permanently named by IUPAC.	[nb 4]
Uus	Ununseptium	117	Temporary name given to tennessine until it was permanently named by IUPAC.	[nb 4]
Uut	Ununtrium	113	Temporary name given to nihonium until it was permanently named by IUPAC.	[nb 4]
Uuu	Unununium	111	Temporary name given to roentgenium until it was permanently named by IUPAC.	[nb 4]
Ur	Uranium	92	Current symbol is U.	[nb 1]
Vi	Virginium	87	Discredited claim to discovery of francium.	[nb 2]	[7]
Vm	Virginium	87	Discredited claim to discovery of francium.	[nb 2]	[7]
Va	Vanadium	23	Current symbol is V.	[nb 1]
Wo	Tungsten	74	Current symbol is W.	[nb 1]
X	Xenon	54	Current symbol is Xe. The symbol is now used for halogens.	[nb 1]
Yt	Yttrium	39	Current symbol is Y.	[nb 1]	[7]

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.[11]

Chemical symbol	Original name	Modern name	Atomic number	Origin of symbol
☉	Hydrogen	Hydrogen	1	Daltonian symbol circa 1808.
⬤	Carbon	Carbon	6	Daltonian symbol circa 1808.
⦶	Azote	Nitrogen	7	Daltonian symbol circa 1808.
◯	Oxygen	Oxygen	8	Daltonian symbol circa 1808.
⦷	Soda	Sodium	11	Daltonian symbol circa 1808.
⊛	Magnesium	Magnesium	12	Alchemical symbol. Also adopted as the symbol for Magnesium by Dalton in 1808.
🟕	Silicon	Silicon	14	Daltonian symbol circa 1808.
	Sulfur	Sulfur	16	Alchemical symbol.
	Pallas	Sulfur	16	Alchemical symbol.
🜍	Sulfur	Sulfur	16	Alchemical symbol.
ⴲ	Sulfur	Sulfur	16	Daltonian symbol circa 1808.
⦾	Calcium	Calcium	20	Daltonian symbol circa 1808.
♂	Mars	Iron	26	Alchemical symbol.
Ⓘ	Iron	Iron	26	Daltonian symbol circa 1808.
Ⓝ	Nickel	Nickel	28	Daltonian symbol circa 1808.
	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.
Ⓩ	Zinc	Zinc	30	Daltonian symbol circa 1808.
	Arsenic	Arsenic	33	Alchemical symbol.
🜺	Arsenic	Arsenic	33	Alchemical symbol.
⊕	Yttrium	Yttrium	39	Daltonian symbol circa 1808.
☽	Luna	Silver	47	Alchemical symbol.
🜛	Silver	Silver	47	Alchemical symbol.
Ⓢ	Silver	Silver	47	Daltonian symbol circa 1808.
♃	Iupiter	Tin	50	Alchemical symbol.
Ⓣ	Tin	Tin	50	Daltonian symbol circa 1808.
♁	Antimony	Antimony	51	Alchemical symbol.
☉☾	Platinum	Platinum	78	Alchemical symbol.
⛢	Uranus	Platinum	78	Alchemical symbol.
Ⓟ	Platinum	Platinum	78	Daltonian symbol circa 1808.
☼	Sol	Gold	79	Alchemical symbol from the 16th century.
☉	Sol	Gold	79	Alchemical symbol from 1700 through 1783.
🜚	Gold	Gold	79	Alchemical symbol.
Ⓖ	Gold	Gold	79	Daltonian symbol circa 1808.
♓︎	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.
Ⓛ	Lead	Lead	82	Daltonian symbol circa 1808.
♉︎	Taurus	Bismuth	83	Alchemical symbol.
Ⓑ	Bismuth	Bismuth	83	Daltonian symbol circa 1808.
Ⓤ	Uranium	Uranium	92	Daltonian symbol circa 1808.

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, as is thoron (Tn) for radon-220 (though not actinon; An is usually used instead for 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 and C₆D₆ can be used instead of [²H₆]C₆H₆.[12]

The symbols for isotopes of elements other than hydrogen and radon 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 decay chains of actinium, radium, and thorium) bear placeholder names using the early naming system devised by Ernest Rutherford.[13]

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 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 ^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

General:

A: A deprotonated acid or an anion
An: any actinide
B: A base, often in the context of Lewis acid–base theory or Brønsted–Lowry acid–base theory
E: any element or electrophile
L: any ligand
Ln: any lanthanide
M: any metal
Mm: mischmetall (occasionally used)[14]
Ng: any noble gas (Rg is sometimes used, but that is also used for the element roentgenium: see above)
Nu: any nucleophile
R: any unspecified radical (moiety) not important to the discussion
St: steel (occasionally used)
X: any halogen (or sometimes pseudohalogen)

From organic chemistry:

Ac: acetyl – (also used for the element actinium: see above)
Ad: 1-adamantyl
All: allyl
Am: amyl (pentyl) – (also used for the element americium: see above)
Ar: aryl – (also used for the element argon: see above)
Bn: benzyl
Bs: brosyl or (outdated) benzenesulfonyl
Bu: butyl (i-, s-, or t- prefixes may be used to denote iso-, sec-, or tert- isomers, respectively)
Bz: benzoyl
Cp: cyclopentadienyl
Cp*: pentamethylcyclopentadienyl
Cy: cyclohexyl
Cyp: cyclopentyl
Et: ethyl
Me: methyl
Mes: mesityl (2,4,6-trimethylphenyl)
Ms: mesyl (methylsulfonyl)
Np: neopentyl – (also used for the element neptunium: see above)
Ns: nosyl
Pent: pentyl
Ph, Φ: phenyl
Pr: propyl – (i- prefix may be used to denote isopropyl. Also used for the element praseodymium: see above)
R: In organic chemistry contexts, an unspecified "R" is often understood to be an alkyl group
Tf: triflyl (trifluoromethanesulfonyl)
Tr, Trt: trityl (triphenylmethyl)
Ts, Tos: tosyl (para-toluenesulfonyl) – (Ts also used for the element tennessine: see above)
Vi: vinyl

Exotic atoms:

Notes

Name changed due to a standardization of, modernization of, or update to older formerly-used symbol.
Name designated by discredited/disputed claimant.
Name proposed prior to discovery/creation of element or prior to official re-naming of a placeholder name.
Temporary placeholder name.

References

IUPAC Provisional Recommendations: IR-3: Elements and Groups of Elements (PDF) (Report). IUPAC. March 2004.
"Periodic Table – Royal Society of Chemistry". www.rsc.org.
"Online Etymology Dictionary". etymonline.com.
Wieser, Michael E.; et al. (2013). Atomic weights of the elements 2011 (IUPAC Technical Report). Pure Appl. Chem. (Report). 85. pp. 1047–1078. doi:10.1351/PAC-REP-13-03-02. (for standard atomic weights of elements)
Sonzogni, Alejandro. "Interactive Chart of Nuclides". National Nuclear Data Center: Brookhaven National Laboratory. Retrieved 2008-06-06. (for atomic weights of elements with atomic numbers 103–118)
Holden, N. E. (12 March 2004). "History of the Origin of the Chemical Elements and Their Discoverers". National Nuclear Data Center.
Leal, João P. (2013). "The Forgotten Names of Chemical Elements". Foundations of Science. 19 (2): 175–183. doi:10.1007/s10699-013-9326-y.
"Fred Allison". Encyclopedia of Alabama.
Fontani, Marco; Costa, Mariagrazia; Orna, Mary Virginia (2014). The Lost Elements: The Periodic Table's Shadow Side. Oxford University Press. ISBN 9780199383344.
Praseodymium on was.chemistryexplained.com.
Berzelius, Jöns Jakob. "Essay on the Cause of Chemical Proportions, and on Some Circumstances Relating to Them: Together with a Short and Easy Method of Expressing Them." Annals of Philosophy 2, Pp.443–454 (1813); 3, Pp.51–52, 93–106, 244–255, 353–364 (1814); (Subsequently republished in "A Source Book in Chemistry, 1400-1900", eds. Leicester, Henry M. & Herbert S. Klickstein. 1952.)
IUPAC. "Isotopically Modified Compounds". IUPAC. Retrieved 31 March 2015.
Morgan, G. T., ed. (1905). "Annual Reports on the Progress of Chemistry for 1904". Journal of the Chemical Society. Gurney & Jackson. 1: 268. In view of the extraordinarily complex nature of the later changes occurring in Radium, Rutherford has proposed a new and convenient system of nomenclature. The first product of the change of the radium emanation is named radium A, the next radium B, and so on.
Jurczyk, M.; Rajewski, W.; Majchrzycki, W.; Wójcik, G. (1999-08-30). "Mechanically alloyed MmNi₅-type materials for metal hydride electrodes". Journal of Alloys and Compounds. 290 (1–2): 262–266. doi:10.1016/S0925-8388(99)00202-9.

Elementymology & Elements Multidict, 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)
Committee on Nomenclature, Terminology, and Symbols, American Chemical Society

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[fn10-2] Z is the standard symbol for atomic number

[fn2-7] The isotopic composition of this element varies in some geological specimens, and the variation may exceed the uncertainty stated in the table.

[fn3-8] The isotopic composition of the element can vary in commercial materials, which can cause the atomic weight to deviate significantly from the given value.

[fn4-9] The isotopic composition varies in terrestrial material such that a more precise atomic weight can not be given.

[fn9-10] The value listed is the conventional atomic-weight value suitable for trade and commerce. The actual value may differ depending on the isotopic composition of the sample. Since 2009, IUPAC provides the standard atomic-weight values for these elements using the interval notation. The corresponding standard atomic weights are:
Hydrogen: [1.00784, 1.00811]

Lithium: [6.938, 6.997]

Boron: [10.806, 10.821]

Carbon: [12.0096, 12.0116]

Nitrogen: [14.00643, 14.00728]

Oxygen: [15.99903, 15.99977]

Magnesium: [24.304, 24.307]

Silicon: [28.084, 28.086]

Sulfur: [32.059, 32.076]

Chlorine: [35.446, 35.457]

Argon: [39.792, 39.963]

Bromine: [79.901, 79.907]

Thallium: [204.382, 204.385]

[6] Hydrogen: [1.00784, 1.00811]

[7] Lithium: [6.938, 6.997]

[8] Boron: [10.806, 10.821]

[9] Carbon: [12.0096, 12.0116]

[10] Nitrogen: [14.00643, 14.00728]

[11] Oxygen: [15.99903, 15.99977]

[12] Magnesium: [24.304, 24.307]

[13] Silicon: [28.084, 28.086]

[14] Sulfur: [32.059, 32.076]

[15] Chlorine: [35.446, 35.457]

[16] Argon: [39.792, 39.963]

[17] Bromine: [79.901, 79.907]

[18] Thallium: [204.382, 204.385]

[fn5-11] The atomic weight of commercial lithium can vary between 6.939 and 6.996—analysis of the specific material is necessary to find a more accurate value.

[fn1-12] The element does not have any stable nuclides, and a value in brackets, e.g. [209], indicates the mass number of the longest-lived isotope of the element. However, four such elements, bismuth, thorium, protactinium, and uranium, have characteristic terrestrial isotopic compositions, and thus their standard atomic weights are given.

[why_not_used6-13] Name changed due to a standardization of, modernization of, or update to older formerly-used symbol.

[why_not_used7-15] Name designated by discredited/disputed claimant.

[why_not_used8-18] Name proposed prior to discovery/creation of element or prior to official re-naming of a placeholder name.

[why_not_used9-21] Temporary placeholder name.

[1] IUPAC Provisional Recommendations: IR-3: Elements and Groups of Elements (PDF) (Report). IUPAC. March 2004.

[3] "Periodic Table – Royal Society of Chemistry". www.rsc.org.

[4] "Online Etymology Dictionary". etymonline.com.

[5] Wieser, Michael E.; et al. (2013). Atomic weights of the elements 2011 (IUPAC Technical Report). Pure Appl. Chem. (Report). 85. pp. 1047–1078. doi:10.1351/PAC-REP-13-03-02. (for standard atomic weights of elements)

[6] Sonzogni, Alejandro. "Interactive Chart of Nuclides". National Nuclear Data Center: Brookhaven National Laboratory. Retrieved 2008-06-06. (for atomic weights of elements with atomic numbers 103–118)

[Holden2004-14] Holden, N. E. (12 March 2004). "History of the Origin of the Chemical Elements and Their Discoverers". National Nuclear Data Center.

[leal-16] Leal, João P. (2013). "The Forgotten Names of Chemical Elements". Foundations of Science. 19 (2): 175–183. doi:10.1007/s10699-013-9326-y.

[encyclopediaofalabama.org-17] "Fred Allison". Encyclopedia of Alabama.

[Fontanietal-19] Fontani, Marco; Costa, Mariagrazia; Orna, Mary Virginia (2014). The Lost Elements: The Periodic Table's Shadow Side. Oxford University Press. ISBN 9780199383344.

[chemistryexplained-20] Praseodymium on was.chemistryexplained.com.

[22] Berzelius, Jöns Jakob. "Essay on the Cause of Chemical Proportions, and on Some Circumstances Relating to Them: Together with a Short and Easy Method of Expressing Them." Annals of Philosophy 2, Pp.443–454 (1813); 3, Pp.51–52, 93–106, 244–255, 353–364 (1814); (Subsequently republished in "A Source Book in Chemistry, 1400-1900", eds. Leicester, Henry M. & Herbert S. Klickstein. 1952.)

[SectionH-23] IUPAC. "Isotopically Modified Compounds". IUPAC. Retrieved 31 March 2015.

[24] Morgan, G. T., ed. (1905). "Annual Reports on the Progress of Chemistry for 1904". Journal of the Chemical Society. Gurney & Jackson. 1: 268. In view of the extraordinarily complex nature of the later changes occurring in Radium, Rutherford has proposed a new and convenient system of nomenclature. The first product of the change of the radium emanation is named radium A, the next radium B, and so on.

[25] Jurczyk, M.; Rajewski, W.; Majchrzycki, W.; Wójcik, G. (1999-08-30). "Mechanically alloyed MmNi₅-type materials for metal hydride electrodes". Journal of Alloys and Compounds. 290 (1–2): 262–266. doi:10.1016/S0925-8388(99)00202-9.