Question

The magnitude of the electrostatic force between two identical ions that are separated by a
distance of 5.0x10-10 m is 3.7x10-9 N. (a) What is the charge of each ion? (b) How many
electrons are “missing” from each ion (thus giving the ion its charge imbalance)?

Answer 1

(a) Charge on each ion: $q=2e$

(b) Two electrons are missing  

Explanation:

(a) We have,

$r = 5.0*10^{-10}\\ \\F_q = 3.7*10^{-9} \\ \\ F_q=\frac{kq^2}{r^2}\\ \\=>3.7*10^{-9}=\frac{9*10^{9}*q^2}{(5*10^{-10})^2}\\ \\=>q=\pm 3.2*10^{-19} C=2e$

(b) Here, Charge can be both negative or positive but we can talking about missing electrons ,then we consider charge to be positive.

Hence,

Ion Becomes $A^{2+}$

This means Charge loses 2 electrons to obtain stable configuration.

That is, 2 electrons are missing which  gave rise to charge imbalance.