Howwould youexplainthe fact thethat thefirstionizationenthalpyof sodiumis lowerthan thatofmagnesium but itssecondionizationenthalpyis higherthan that of magnesium ?

Howwould youexplainthe fact thethat thefirstionizationenthalpyof sodiu

1.	Howwould youexplainthe fact thethat thefirstionizationenthalpyof sodiumis lowerthan thatofmagnesium but itssecondionizationenthalpyis higherthan that of magnesium ?
Answer» Solution :The E.C.Of Na is `1s^(2)2s^(2)2p^(6)3s^(1)` and E.C.Of Mg is `1s^(2)2s^(2)2p^(6)3s^(2)` . In boththe casesfirstelectronis to be removedfrom the 3sorbitalbut nuclearcharge ofMg (+2)is hgiherthan thatof Na (+11). Furthermore 3s-orbital in Mg iscompletelyfilled(morestable )while INNA itis onlyhalf- filled (less STABLE ) . THEREFORE`Delta_(i) H` of Na islowerthan thatof Mg. `Na (1 s^(2)2s^(2)2p^(6) 3s^(1))OVERSET(Delta_(i)H_(1))(to)Na^(+) (1s^(2)2s^(2)2p^(6)) overset(Delta_(i)H_(2))(to)Na^(2+) (1s^(2) 2s^(2) 2p^(5))` Neongasconfiguration (morestable ) `Mg (1s^(2) 2s^(2)2p^(6)3s^(2)) overset(Delta_(i) H_(1))(to)Mg^(+) (1s^(2)2s^(2)2p^(6)3s^(1))overset(Delta_(i)H_(2))(to)Mg^(2+)(1s^(2) 2s^(2) 2p^(6))` Neongas CONFIGURATION (more stable) Afterthe removal of thethe firstelectron`Na^(+)` acquiredthe morestable neon gas configuration. Thus for the secondelectronfrom Nais to beremovedfrom thestablenoble(i.e.,neon ) gasconfigurationbutthe lossof secondelectronfrom Mggivesthe morestableneongas configuration.Thus `Delta_(i) H_(2)` of Na is more than`Delta_(i)H_(2)` of Mg.