Logo of the Atomic Weights Commission Logo of the International Union of Pure and Applied Chemistry

Current atomic masses

Atomic masses of isotopes are evaluated by IUPAP and below is the latest Atomic Mass Evaluation report, dated 2016. All atomic masses of nuclides, ma, are expressed in daltons (symbol Da), which is 1/12 mass of a single carbon-12 atom (unbound, neutral, in its electronic and nuclear ground state, and at rest).

Atomic Masses used by CIAAW (2016)

Z Symbol Element A Atomic mass,
ma/Da
1 H hydrogen 1   1.007 825 0322(6)
2   2.014 101 7781(8)
2 He helium 3   3.016 029 322(2)
4   4.002 603 2545(4)
3 Li lithium 6   6.015 122 89(1)
7   7.016 003 44(3)
4 Be beryllium 9   9.012 1831(5)
5 B boron 10  10.012 9369(1)
11  11.009 305 17(8)
6 C carbon 12  12(exact)
13  13.003 354 835(2)
7 N nitrogen 14  14.003 074 004(2)
15  15.000 108 899(4)
8 O oxygen 16  15.994 914 619(1)
17  16.999 131 757(5)
18  17.999 159 613(5)
9 F fluorine 19  18.998 403 163(6)
10 Ne neon 20  19.992 440 18(1)
21  20.993 8467(3)
22  21.991 3851(1)
11 Na sodium 23  22.989 769 28(2)
12 Mg magnesium 24  23.985 041 70(9)
25  24.985 8370(3)
26  25.982 5930(2)
13 Al aluminium 27  26.981 5384(3)
14 Si silicon 28  27.976 926 535(3)
29  28.976 494 665(4)
30  29.973 7701(2)
15 P phosphorous 31  30.973 761 998(5)
16 S sulfur 32  31.972 071 174(9)
33  32.971 458 91(1)
34  33.967 8670(3)
36  35.967 081(2)
17 Cl chlorine 35  34.968 8527(3)
37  36.965 9026(4)
18 Ar argon 36  35.967 5451(2)
38  37.962 732(2)
40  39.962 383 12(2)
19 K potassium 39  38.963 706 49(3)
40*  39.963 9982(4)
41  40.961 825 26(3)
20 Ca calcium 40  39.962 5909(2)
42  41.958 618(1)
43  42.958 766(2)
44  43.955 481(2)
46  45.953 69(2)
48*  47.952 5229(6)
21 Sc scandium 45  44.955 908(5)
22 Ti titanium 46  45.952 627(1)
47  46.951 7577(8)
48  47.947 9409(8)
49  48.947 8646(8)
50  49.944 7858(8)
23 V vanadium 50*  49.947 156(3)
51  50.943 957(3)
24 Cr chromium 50  49.946 041(3)
52  51.940 505(3)
53  52.940 647(3)
54  53.938 878(3)
25 Mn manganese 55  54.938 043(2)
26 Fe iron 54  53.939 608(3)
56  55.934 936(2)
57  56.935 392(2)
58  57.933 274(3)
27 Co cobalt 59  58.933 194(3)
28 Ni nickel 58  57.935 342(3)
60  59.930 785(3)
61  60.931 055(3)
62  61.928 345(3)
64  63.927 966(3)
29 Cu copper 63  62.929 597(3)
65  64.927 790(5)
30 Zn zinc 64  63.929 142(5)
66  65.926 034(5)
67  66.927 127(5)
68  67.924 844(5)
70  69.925 32(2)
31 Ga gallium 69  68.925 573(8)
71  70.924 702(6)
32 Ge germanium 70  69.924 249(6)
72  71.922 0758(5)
73  72.923 4590(4)
74  73.921 177 76(8)
76*  75.921 4027(1)
33 As arsenic 75  74.921 595(6)
34 Se selenium 74  73.922 4759(1)
76  75.919 2137(1)
77  76.919 9141(5)
78  77.917 309(1)
80  79.916 522(6)
82*  81.916 699(3)
35 Br bromine 79  78.918 338(7)
81  80.916 288(6)
36 Kr krypton 78*  77.920 366(2)
80  79.916 378(5)
82  81.913 481 15(4)
83  82.914 126 52(6)
84  83.911 497 73(3)
86  85.910 610 63(3)
37 Rb rubidium 85  84.911 789 74(3)
87*  86.909 180 53(4)
38 Sr strontium 84  83.913 419(8)
86  85.909 260 73(4)
87  86.908 877 50(3)
88  87.905 612 26(4)
39 Y yttrium 89  88.905 84(1)
40 Zr zirconium 90  89.904 6988(8)
91  90.905 6402(7)
92  91.905 0353(7)
94  93.906 313(1)
96*  95.908 2776(8)
41 Nb niobium 93  92.906 37(1)
42 Mo molybdenum 92  91.906 807(1)
94  93.905 084(1)
95  94.905 8374(8)
96  95.904 6748(8)
97  96.906 017(1)
98  97.905 404(1)
100*  99.907 468(2)
44 Ru ruthenium 96  95.907 589(1)
98  97.905 29(5)
99  98.905 930(3)
100  99.904 211(3)
101 100.905 573(3)
102 101.904 340(3)
104 103.905 43(2)
45 Rh rhodium 103 102.905 49(2)
46 Pd palladium 102 101.905 632(4)
104 103.904 030(9)
105 104.905 079(8)
106 105.903 480(8)
108 107.903 892(8)
110 109.905 173(5)
47 Ag silver 107 106.905 09(2)
109 108.904 756(9)
48 Cd cadmium 106 105.906 460(8)
108 107.904 184(8)
110 109.903 008(3)
111 110.904 184(3)
112 111.902 764(2)
113* 112.904 408(2)
114 113.903 365(2)
116* 115.904 763(1)
49 In indium 113 112.904 060(2)
115* 114.903 878 77(8)
50 Sn tin 112 111.904 825(2)
114 113.902 7801(2)
115 114.903 3447(1)
116 115.901 7428(6)
117 116.902 954(3)
118 117.901 607(3)
119 118.903 311(5)
120 119.902 202(6)
122 121.903 44(2)
124 123.905 277(7)
51 Sb antimony 121 120.903 81(2)
123 122.904 21(1)
52 Te tellurium 120 119.904 06(2)
122 121.903 04(1)
123 122.904 27(1)
124 123.902 82(1)
125 124.904 43(1)
126 125.903 31(1)
128* 127.904 461(6)
130* 129.906 222 75(8)
53 I iodine 127 126.904 47(3)
54 Xe xenon 124 123.905 89(1)
126 125.904 30(3)
128 127.903 531(7)
129 128.904 780 86(4)
130 129.903 509 35(6)
131 130.905 084 14(6)
132 131.904 155 09(4)
134 133.905 393 03(6)
136* 135.907 214 48(5)
55 Cs caesium 133 132.905 451 96(6)
56 Ba barium 130* 129.906 32(2)
132 131.905 061(7)
134 133.904 508(2)
135 134.905 689(2)
136 135.904 576(2)
137 136.905 827(2)
138 137.905 247(2)
57 La lanthanum 138* 137.907 12(2)
139 138.906 36(2)
58 Ce cerium 136 135.907 129(3)
138 137.905 99(3)
140 139.905 45(1)
142 141.909 25(2)
59 Pr praseodymium 141 140.907 66(1)
60 Nd neodymium 142 141.907 73(1)
143 142.909 82(1)
144* 143.910 09(1)
145 144.912 58(1)
146 145.913 12(1)
148 147.916 90(2)
150* 149.920 902(9)
62 Sm samarium 144 143.912 01(1)
147* 146.914 90(1)
148* 147.914 83(1)
149 148.917 191(9)
150 149.917 282(9)
152 151.919 739(8)
154 153.922 22(1)
63 Eu europium 151* 150.919 857(9)
153 152.921 237(9)
64 Gd gadolinium 152 151.919 799(8)
154 153.920 873(8)
155 154.922 630(8)
156 155.922 131(8)
157 156.923 968(8)
158 157.924 112(8)
160 159.927 062(9)
65 Tb terbium 159 158.925 354(8)
66 Dy dysprosium 156 155.924 284(8)
158 157.924 41(2)
160 159.925 203(5)
161 160.926 939(5)
162 161.926 804(5)
163 162.928 737(5)
164 163.929 181(5)
67 Ho holmium 165 164.930 328(7)
68 Er erbium 162 161.928 787(6)
164 163.929 207(5)
166 165.930 299(8)
167 166.932 054(8)
168 167.932 376(8)
170 169.935 47(1)
69 Tm thulium 169 168.934 218(6)
70 Yb ytterbium 168 167.933 889(8)
170 169.934 767 25(7)
171 170.936 331 52(9)
172 171.936 386 66(9)
173 172.938 216 22(8)
174 173.938 867 55(8)
176 175.942 5747(1)
71 Lu lutetium 175 174.940 777(8)
176* 175.942 692(8)
72 Hf hafnium 174* 173.940 05(2)
176 175.941 41(1)
177 176.943 23(1)
178 177.943 71(1)
179 178.945 83(1)
180 179.946 56(1)
73 Ta tantalum 180* 179.947 47(2)
181 180.948 00(1)
74 W tungsten 180* 179.946 71(1)
182 181.948 206(5)
183 182.950 224(5)
184 183.950 933(5)
186 185.954 365(8)
75 Re rhenium 185 184.952 958(6)
187* 186.955 752(5)
76 Os osmium 184* 183.952 493(6)
186* 185.953 838(5)
187 186.955 750(5)
188 187.955 837(5)
189 188.958 146(5)
190 189.958 446(5)
192 191.961 48(2)
77 Ir iridium 191 190.960 591(9)
193 192.962 924(9)
78 Pt platinum 190* 189.959 950(5)
192 191.961 04(2)
194 193.962 683(3)
195 194.964 794(3)
196 195.964 955(3)
198 197.967 90(2)
79 Au gold 197 196.966 570(4)
80 Hg mercury 196 195.965 83(2)
198 197.966 769(3)
199 198.968 281(4)
200 199.968 327(4)
201 200.970 303(5)
202 201.970 644(5)
204 203.973 494(3)
81 Tl thallium 203 202.972 344(8)
205 204.974 427(8)
82 Pb lead 204 203.973 043(8)
206 205.974 465(8)
207 206.975 897(8)
208 207.976 652(8)
83 Bi bismuth 209* 208.980 40(1)
90 Th thorium 230* 230.033 132(8)
232* 232.038 05(1)
91 Pa protactinium 231* 231.035 88(1)
92 U uranium 234* 234.040 950(8)
235* 235.043 928(8)
238* 238.050 79(1)
Z Symbol Element A Atomic mass,
ma/Da

Footnote      Back to Top
Radioactive isotope.

CIAAW uses nuclide masses as reported in the Atomic Mass Evaluation reports. However, the uncertainty of the nuclide masses is not taken as reported. Rather, all uncertainty estimates are expanded by a factor of k = 6 in order to conform to the conservative reporting practices of CIAAW.

Adapted from

M. Wang et al
The Ame2016 Atomic Mass Evaluation Chinese Physics C, 2017 (41) 030003

CIAAW uses nuclide masses as reported in the Atomic Mass Evaluation reports. However, the uncertainty of the nuclide masses is not taken as reported. Rather, all uncertainty estimates are expanded by a factor of k = 6 in order to conform to the conservative reporting practices of CIAAW.

Last updated: 21 Aug 2018