Question

Show that the following species have the same number of electron Na, Mg, O, and Ne​

Answer 1

in its neutral state an atom of Na has 11 electrons so when it loses an electron it becomes Na^+ with 10 electrons.

a neutral atom of Mg has 12 electrons by losing 2 elections it becomes Mg^2+ with 10 electrons

a neutral atom of oxygen has 8 electrons if it gains 2 electrons it becomes O^2- with 10 electrons

a neutral atom of Ne has 10 electrons

All of the above species in their excited states has 10 electrons (except for Ne which has 10 electrons in its neutral state) so they are all isoelectronic with Na^+