Atomic Masses

APPENDIX B

Atomic Masses Relative Atomic Mass and Isotopic Compositions. Only the most common and most stable of the heavy elements are given. (From the NIST web pages.)

Isotope 1

2

3

Mass

Percent

H

1

1.007825

99.99

D

2

2.014102

0.01

T

3

3.016049

He

3

3.016029

4

4.002603

Li

0.00

0.27

22

21.991386

9.25

11

Na

23

22.989770

100

12

Mg

24

23.985042

78.99

7

7.016004

92.41

26

25.982593

11.01

10.012937

19.9

11

11.009306

80.1

F

20.993847

10.00

10

9

21

24.985837

B

O

90.48

25

5

8

19.992440

7.59

9.012182

N

20

6.015122

9

7

Ne

Percent

6

Be

C

10

Mass

100.0

4

6

Isotope

100

12

12.000000

98.93

13

13.003355

1.07

14

14.003241

13

Al

27

26.981538

100

14

Si

28

27.976927

92.23

29

28.976495

4.68

30

29.973770

3.09

15

P

31

30.973762

100

16

S

32

31.972071

94.93

14

14.003074

99.63

33

32.971459

0.76

15

15.000109

0.37

34

33.967867

4.29

36

35.967081

0.02

35

34.968853

75.78

37

36.965903

24.22

36

35.967546

0.34

38

37.962732

0.06

49

39.962383

99.60

16

15.994915

99.75

17

16.999132

0.038

18

17.999160

0.205

19

18.998403

100

17

18

Cl

Ar

421