Periodic table of atomic mass

Interactive periodic table of atomic mass in atomic mass units (u). ElementWorks is a free interactive periodic table: hover an element to preview it, click it for its full card, or pick another view from the Show menu.

Periodic table of atomic mass explained

Atomic mass is the average mass of an element’s atoms, weighted by the natural abundance of its isotopes, in atomic mass units (u). It is the number you use for molar mass: an element’s atomic mass in u equals its molar mass in g/mol. For elements with no stable isotopes the value is the mass number of the longest-lived isotope.

Highest values

Lawrencium (Lr): 266 u
Nobelium (No): 259 u
Mendelevium (Md): 258 u
Fermium (Fm): 257 u
Einsteinium (Es): 252 u

Lowest values

Hydrogen (H): 1.008 u
Helium (He): 4.003 u
Lithium (Li): 6.94 u
Beryllium (Be): 9.012 u
Boron (B): 10.81 u

Data table

Show the full data table (all 118 elements)

Atomic mass (u) of all 118 elements
No.	Symbol	Element	Atomic mass (u)
1	H	Hydrogen	1.008 u
2	He	Helium	4.003 u
3	Li	Lithium	6.94 u
4	Be	Beryllium	9.012 u
5	B	Boron	10.81 u
6	C	Carbon	12.011 u
7	N	Nitrogen	14.007 u
8	O	Oxygen	15.999 u
9	F	Fluorine	18.998 u
10	Ne	Neon	20.18 u
11	Na	Sodium	22.99 u
12	Mg	Magnesium	24.305 u
13	Al	Aluminium	26.982 u
14	Si	Silicon	28.085 u
15	P	Phosphorus	30.974 u
16	S	Sulfur	32.06 u
17	Cl	Chlorine	35.45 u
18	Ar	Argon	39.948 u
19	K	Potassium	39.098 u
20	Ca	Calcium	40.078 u
21	Sc	Scandium	44.956 u
22	Ti	Titanium	47.867 u
23	V	Vanadium	50.942 u
24	Cr	Chromium	51.996 u
25	Mn	Manganese	54.938 u
26	Fe	Iron	55.845 u
27	Co	Cobalt	58.933 u
28	Ni	Nickel	58.693 u
29	Cu	Copper	63.546 u
30	Zn	Zinc	65.382 u
31	Ga	Gallium	69.723 u
32	Ge	Germanium	72.631 u
33	As	Arsenic	74.922 u
34	Se	Selenium	78.972 u
35	Br	Bromine	79.904 u
36	Kr	Krypton	83.798 u
37	Rb	Rubidium	85.468 u
38	Sr	Strontium	87.621 u
39	Y	Yttrium	88.906 u
40	Zr	Zirconium	91.224 u
41	Nb	Niobium	92.906 u
42	Mo	Molybdenum	95.951 u
43	Tc	Technetium	98 u
44	Ru	Ruthenium	101.072 u
45	Rh	Rhodium	102.906 u
46	Pd	Palladium	106.421 u
47	Ag	Silver	107.868 u
48	Cd	Cadmium	112.414 u
49	In	Indium	114.818 u
50	Sn	Tin	118.711 u
51	Sb	Antimony	121.76 u
52	Te	Tellurium	127.603 u
53	I	Iodine	126.904 u
54	Xe	Xenon	131.294 u
55	Cs	Cesium	132.905 u
56	Ba	Barium	137.328 u
57	La	Lanthanum	138.905 u
58	Ce	Cerium	140.116 u
59	Pr	Praseodymium	140.908 u
60	Nd	Neodymium	144.242 u
61	Pm	Promethium	145 u
62	Sm	Samarium	150.362 u
63	Eu	Europium	151.964 u
64	Gd	Gadolinium	157.253 u
65	Tb	Terbium	158.925 u
66	Dy	Dysprosium	162.5 u
67	Ho	Holmium	164.93 u
68	Er	Erbium	167.259 u
69	Tm	Thulium	168.934 u
70	Yb	Ytterbium	173.045 u
71	Lu	Lutetium	174.967 u
72	Hf	Hafnium	178.492 u
73	Ta	Tantalum	180.948 u
74	W	Tungsten	183.841 u
75	Re	Rhenium	186.207 u
76	Os	Osmium	190.233 u
77	Ir	Iridium	192.217 u
78	Pt	Platinum	195.085 u
79	Au	Gold	196.967 u
80	Hg	Mercury	200.592 u
81	Tl	Thallium	204.38 u
82	Pb	Lead	207.21 u
83	Bi	Bismuth	208.98 u
84	Po	Polonium	209 u
85	At	Astatine	210 u
86	Rn	Radon	222 u
87	Fr	Francium	223 u
88	Ra	Radium	226 u
89	Ac	Actinium	227 u
90	Th	Thorium	232.038 u
91	Pa	Protactinium	231.036 u
92	U	Uranium	238.029 u
93	Np	Neptunium	237 u
94	Pu	Plutonium	244 u
95	Am	Americium	243 u
96	Cm	Curium	247 u
97	Bk	Berkelium	247 u
98	Cf	Californium	251 u
99	Es	Einsteinium	252 u
100	Fm	Fermium	257 u
101	Md	Mendelevium	258 u
102	No	Nobelium	259 u
103	Lr	Lawrencium	266 u
104	Rf	Rutherfordium	267 u
105	Db	Dubnium	268 u
106	Sg	Seaborgium	269 u
107	Bh	Bohrium	270 u
108	Hs	Hassium	269 u
109	Mt	Meitnerium	278 u
110	Ds	Darmstadtium	281 u
111	Rg	Roentgenium	282 u
112	Cn	Copernicium	285 u
113	Nh	Nihonium	286 u
114	Fl	Flerovium	289 u
115	Mc	Moscovium	289 u
116	Lv	Livermorium	293 u
117	Ts	Tennessine	294 u
118	Og	Oganesson	294 u

Frequently asked questions

How do I use atomic mass to find molar mass?

Add up the atomic masses of every atom in the formula. For example, H₂O is 2(1.008) + 15.999 = 18.015 g/mol.

Why is atomic mass not a whole number?

It is a weighted average of the masses of an element’s isotopes, and each isotope’s mass is itself slightly different from a whole number.

Does atomic mass always increase with atomic number?

Almost always. A few pairs, such as argon and potassium, are reversed because of isotope abundances.