The relative atomic mass of boron 10.2. if the element occurs in two isotopic forms, boron-10 and boron-11, what are their geometrical abundances?

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Boron consists of two isotopes, boron-10 and boron-11.

Given that its relative atomic mass is 10.2

Find the abundance of each isotope.

Let y/100 = the abundance of copper-10

and (100 - y) / 100 = the abundance of copper-11

10.2 = (y/100 x 10) + [ (100 - y) / 100 x 11]

10.2 = 10y/100 + 1100/100 - 11y/100

1020 = 10y + 1100 - 11y

-80 = - y

y = 80

Abundance of boron-10 = 10/100 = 10%

Abundance of boron-11 = 100 - 10 = 90%