The electrostatic force between two identical ions that are separated by a distance of is (a) We have to find the charge on each ion. (b) We have to find the number of electrons that are missing from each ion.

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Let the charge on each ion be q C. Separation of the two ions is

The magnitude of electrostatic force on each ion due to the other is

Therefore, by Coulomb’s law we have

And

The magnitude of charge on an electron is

Therefore,

We thus find that 2 electrons are missing from each ion for it to have 2 units of positive charge.