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

Explanation

`(Na^(o+), Mg^(2+))," "Na^(o+)=11-1=10`
`Mg^(2+)=12-2=10`
`Ca^(2+), Ar," " Ca^(2+)=20-2=18`
`Ar=18`
`S^(2-)," " K^(o+), S^(2-)=16+2=18`
`K^(o+)=19-1=18`