The number of neutrons are equal to the number of protons present in the nucleus of two elements and their respective dinegative ions possess 8 electrons in L and M shells respectively . Then the ratio of mass numbers of the two elements is

Options

A. 1:2
B. 2:3
C. 3:4
D. 2:5

Answer

a

Explanation

The electronic configuration of the of the dinegative ion with 8 electrons in valence shell (L shell) is
`X^(-2) to 2,8`
`X = 2,6` (Z), mass number is 16,
`Y^(-2) to 2,8, 8 `
`Y to 2, 8, 6 (Z)`
Mass number is 32 (A) for Y.
atio of mass numbers = 16:32, 1:2