What are thevariousfactorsdue towhichthe ionizationenthalpyof the maingroupelementstendsto decrease down thegroup?

What are thevariousfactorsdue towhichthe ionizationenthalpyof the main

1.	What are thevariousfactorsdue towhichthe ionizationenthalpyof the maingroupelementstendsto decrease down thegroup?
Answer» SOLUTION :Within the maingroupelementsthe ionization enthalpy regularly as we moredown thegroup due to thefollowingtwo FACTORS. (i) Atomic size. On movingdownthe group the atomicsizeincreases graduallydue to theadditionofone newprincipal energyshellat eachsucceedingelement .As aresultthe distanceof thevalenceelectronsfrom thenucleusincreases . Consequently theforceof attraction of thenucleusof the valenceelectronsdecreases and hencethe ionizationenthalpydecreases. (ii) SCREENING effect. Withthe additionof newshells thenumberof innerelectronshellswhichshield the valenceelectronsincreases. In otherwordsthe shieldingeffect of thescreening effectincreases . Asa resultthe force of attractionof thenucleusfor thevalenceelectronsfurtherdecreasesand hence theionizationenthalpydecreases.