Question

Which element may occur as different isotopes. Element 'x' has three isotopes with mass numbers 20, 21 and 22. The fractional abundances are 0.90, 0.01 and 0.09 respectively. The average atomic mass is of the following molecules has the smallest bond angle?​

Answer 1

The average atomic mass =( fractional abundance of first isotope × mass number of first isotope + fractional abundance of 2nd isotope × mass number of 2nd isotope + fractional abundance of 3rd isotope × mass number of 3rd isotope)/(fractional abundance of first isotope + fractional abundance of 2nd isotope + fractional abundance of 3rd isotope)

= (0.9 × 20 + 0.01 × 21 + 0.09 × 22)/(0.9 + 0.01 + 0.09)

=(18 + 0.21 + 1.98)/1

= 20.19

hence, average atomic mass of atom is 20.19.

so, Element X is not other than “Ne”.