Successive (IE) values of three elements of third period are given belowAtomic numbers of X, Y and Z respectively are

For X, (E), is very high, thus X+ attains inert gas configuration. It is Na.Na(11)    ⟶Na++e−[Ne]3s1    [Ne] Stable, (E)2 is very high  For Y,(IE)3 is very high thus, Y2+ attains inert gas configuration . It is MgMg(12)    ⟶Mg2++2e−[Ne]3s2    [Ne] Stable, (IE)3 is very high.  For Z,(IE)1 is very high. It is [Ar].