Question

Tin has 10 isotopes: 112 amu at 0.95%, 114 amu at 0.65%, 115 amu at 0.34%, 116 amu at 14.24%, 117amu at 7.57%, 118 amu at 24.01%, 119 amu at 8.58%, 120 amu at 32.97%, 122 amu at 4.71% and 124 amu at 5.98%.Find the atomic mass of Tin.

Answer 1

To calculate the atomic mass of any chemical element, you must use the following mathematical pattern:

1st: multiply the mass number of each isotope by its percentage.

2nd: sum all the results found in the first step.

3rd: divide the sum found in the second step by 100.

So:

1st: multiply the mass number of each isotope by its percentage.

112 x 0.95 = 106.4

114 x 0.65 = 74.1

115 x 0.34 = 39.1

116 x 14.24 = 1651.84

117 x 7.57 = 885.69

118 x 24.01 = 2833.18

119 x 8.58 = 1021.02

120 x 32.97 = 3956.4

122 x 4.71 = 574.62

124 x 5.98 = 741.52

2nd: sum all the results found in the first step.

106.4 + 74.1 + 39.1 + 1651.84 + 885.69 + 2833.18 + 1021.02 + 3956.4 + 574.62 + 741.52 = 11883.87

3rd: divide the sum found in the second step by 100.

11883.87/100 = 118.8387

Atomic mass of Tin: 118.8387