List of elements by atomic weight

This is a list of chemical elements, sorted by standard atomic weight (most stable isotope for artificial elements) and color coded according to type of element. Each element's atomic number, name, element symbol, and group and period numbers on the periodic table are given. The number in parentheses gives the uncertainty in the "concise notation" defined in the IUPAC reference "whereby standard uncertainty is given in parentheses next to the least significant digits to which it applies", e.g., 1.00794(7) stands for 1.00794 ± 0.00007. For artificial elements the nucleon count of the most stable isotope is listed brackets [] as the atomic mass.

Atomic Number	Name	Symbol	Standard atomic weight	Group	Period
1	Hydrogen	H	1.00794(7)	1	1
2	Helium	He	4.002602(2)	18	1
3	Lithium	Li	6.941(2)	1	2
4	Beryllium	Be	9.012182(3)	2	2
5	Boron	B	10.811(7)	13	2
6	Carbon	C	12.0107(8)	14	2
7	Nitrogen	N	14.0067(2)	15	2
8	Oxygen	O	15.9994(3)	16	2
9	Fluorine	F	18.9984032(5)	17	2
10	Neon	Ne	20.1797(6)	18	2
11	Sodium (Natrium)	Na	22.98976928(2)	1	3
12	Magnesium	Mg	24.3050(6)	2	3
13	Aluminium (Aluminum)	Al	26.9815386(8)	13	3
14	Silicon	Si	28.0855(3)	14	3
15	Phosphorus	P	30.973762(2)	15	3
16	Sulfur	S	32.065(5)	16	3
17	Chlorine	Cl	35.453(2)	17	3
18	Argon	Ar	39.948(1)	18	3
19	Potassium (Kalium)	K	39.0983(1)	1	4
20	Calcium	Ca	40.078(4)	2	4
21	Scandium	Sc	44.955912(6)	3	4
22	Titanium	Ti	47.867(1)	4	4
23	Vanadium	V	50.9415(1)	5	4
24	Chromium	Cr	51.9961(6)	6	4
25	Manganese	Mn	54.938045(5)	7	4
26	Iron (Ferrum)	Fe	55.845(2)	8	4
28	Nickel	Ni	58.6934(4)	10	4
27	Cobalt	Co	58.933195(5)	9	4
29	Copper (Cuprum)	Cu	63.546(3)	11	4
30	Zinc	Zn	65.38(2)	12	4
31	Gallium	Ga	69.723(1)	13	4
32	Germanium	Ge	72.64(1)	14	4
33	Arsenic	As	74.92160(2)	15	4
34	Selenium	Se	78.96(3)	16	4
35	Bromine	Br	79.904(1)	17	4
36	Krypton	Kr	83.798(2)	18	4
37	Rubidium	Rb	85.4678(3)	1	5
38	Strontium	Sr	87.62(1)	2	5
39	Yttrium	Y	88.90585(2)	3	5
40	Zirconium	Zr	91.224(2)	4	5
41	Niobium	Nb	92.90638(2)	5	5
42	Molybdenum	Mo	95.96(2)	6	5
43	Technetium	Tc	[98]	7	5
44	Ruthenium	Ru	101.07(2)	8	5
45	Rhodium	Rh	102.90550(2)	9	5
46	Palladium	Pd	106.42(1)	10	5
47	Silver (Argentum)	Ag	107.8682(2)	11	5
48	Cadmium	Cd	112.411(8)	12	5
49	Indium	In	114.818(3)	13	5
50	Tin (Stannum)	Sn	118.710(7)	14	5
51	Antimony (Stibium)	Sb	121.760(1)	15	5
52	Tellurium	Te	127.60(3)	16	5
53	Iodine	I	126.90447(3)	17	5
54	Xenon	Xe	131.293(6)	18	5
55	Caesium (Cesium)	Cs	132.9054519(2)	1	6
56	Barium	Ba	137.327(7)	2	6
57	Lanthanum	La	138.90547(7)	n/a	6
58	Cerium	Ce	140.116(1)	n/a	6
59	Praseodymium	Pr	140.90765(2)	n/a	6
60	Neodymium	Nd	144.242(3)	n/a	6
61	Promethium	Pm	[145]	n/a	6
62	Samarium	Sm	150.36(2)	n/a	6
63	Europium	Eu	151.964(1)	n/a	6
64	Gadolinium	Gd	157.25(3)	n/a	6
65	Terbium	Tb	158.92535(2)	n/a	6
66	Dysprosium	Dy	162.500(1)	n/a	6
67	Holmium	Ho	164.93032(2)	n/a	6
68	Erbium	Er	167.259(3)	n/a	6
69	Thulium	Tm	168.93421(2)	n/a	6
70	Ytterbium	Yb	173.054(5)	n/a	6
71	Lutetium	Lu	174.9668(1)	3	6
72	Hafnium	Hf	178.49(2)	4	6
73	Tantalum	Ta	180.94788(2)	5	6
74	Tungsten (Wolfram)	W	183.84(1)	6	6
75	Rhenium	Re	186.207(1)	7	6
76	Osmium	Os	190.23(3)	8	6
77	Iridium	Ir	192.217(3)	9	6
78	Platinum	Pt	195.084(9)	10	6
79	Gold (Aurum)	Au	196.966569(4)	11	6
80	Mercury (Hydrargyrum)	Hg	200.59(2)	12	6
81	Thallium	Tl	204.3833(2)	13	6
82	Lead (Plumbum)	Pb	207.2(1)	14	6
83	Bismuth	Bi	208.98040(1)	15	6
84	Polonium	Po	[210]	16	6
85	Astatine	At	[210]	17	6
86	Radon	Rn	[220]	18	6
87	Francium	Fr	[223]	1	7
88	Radium	Ra	[226]	2	7
89	Actinium	Ac	[227]	n/a	7
90	Thorium	Th	232.03806(2)	n/a	7
91	Protactinium	Pa	231.03588(2)	n/a	7
92	Uranium	U	238.02891(3)	n/a	7
93	Neptunium	Np	[237]	n/a	7
94	Plutonium	Pu	[244]	n/a	7
95	Americium	Am	[243]	n/a	7
96	Curium	Cm	[247]	n/a	7
97	Berkelium	Bk	[247]	n/a	7
98	Californium	Cf	[251]	n/a	7
99	Einsteinium	Es	[252]	n/a	7
100	Fermium	Fm	[257]	n/a	7
101	Mendelevium	Md	[258]	n/a	7
102	Nobelium	No	[259]	n/a	7
103	Lawrencium	Lr	[262]	3	7
104	Rutherfordium	Rf	[261]	4	7
105	Dubnium	Db	[262]	5	7
106	Seaborgium	Sg	[266]	6	7
107	Bohrium	Bh	[264]	7	7
108	Hassium	Hs	[277]	8	7
109	Meitnerium	Mt	[268]	9	7
110	Darmstadtium	Ds	[271]	10	7
111	Roentgenium	Rg	[272]	11	7
112	Ununbium	Uub	[285]	12	7
113	Ununtrium	Uut	[284]	13	7
114	Ununquadium	Uuq	[289]	14	7
115	Ununpentium	Uup	[288]	15	7
116	Ununhexium	Uuh	[292]	16	7
118	Ununoctium	Uuo	[294]	18	7

Notes

• 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, three elements, Thorium, Protactinium, and Uranium, have a characteristic terrestrial isotopic composition, and thus their standard atomic weights are given.
• 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 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.

References

• International Union of Pure and Applied Chemistry (2006). "Atomic Weights of the Elements 2005". Pure Appl. Chem. 78 (11): 2051–66. Atomic weights of elements with atomic numbers 1-27, 29, 31-41, 43-69, 72-109 taken from this source.
• IUPAC Standard Atomic Weights Revised (2007). Atomic weights of elements with atomic numbers of 28, 30, 42, 70 & 71 taken from this source.
• WebElements Periodic Table Retrieved June 30, 2005. Atomic weights of elements with atomic numbers of 110-116 taken from this source.