Which of the following are isoelectronic species i.e., having the same number of electrons ? `Na ^(+) , K ^(+), Mg ^(2+) , Ca ^(2+), S ^(2-) Ar ,`

Explanation

`Na ^(+) , Mg ^(2+) ` are isoelectronic species whereas `K ^(+) , Ca ^(2+) , S ^(2-) ,` Ar are isoelectronic species.