Amongthe secondperiodelements the actualionizationenergiesare in theorder : Li lt B lt Be lt C lt O lt Nlt F lt Ne. Explainwhy (i)Be hashigher Delta_(i)H than B (ii)O haslowerDelta_(i)H than N and F ?

Amongthe secondperiodelements the actualionizationenergiesare in theor

1.	Amongthe secondperiodelements the actualionizationenergiesare in theorder : Li lt B lt Be lt C lt O lt Nlt F lt Ne. Explainwhy (i)Be hashigher Delta_(i)H than B (ii)O haslowerDelta_(i)H than N and F ?
Answer» Solution :(i) Theionizationenthalpyamong otherthingsdependsupon thetype ofelectronto beremovedfromthe sameprincipal shell. In CASEOF Be `(1 s^(2) 2 s^(2))` the outermostare morestrongly attractedby thenucleus than 2p- electron, thereforelesser amountof energyis required toknockout a 2p- electron than a 2S- electron . Consequently `Delta_(i) H` of Be ishigherthan that`Delta_(i)H` of B. (ii)The electronicconfigurationof `N (1 s^(2) 2s^(2)2p_(x)^(1) 2p_(y)^(1) 2p_(Z)^(1))` in which2p-orbitalsare exactlyhalf- FILLED ismore stablethan theelectronicconfigurationof `O(1 s^(2) 2s^(2)2p_(x)^(2) 2p_(y)^(1) 2p_(z)^(1))` in which a the 2p-orbitals are neitherexactlyhalf - fillednorcompletelyfilled. Thereforeit isdifficult to remove anelectron from N than fromO. As aresult `Delta_(i)H` of N ishigherthan thatof O. Furtherthe electronic configurationof F is `1 s^(2)2s^(2)2p_(x)^(2) 2p_(y)^(2) 2p_(z)^(1)`. Because ofhighernuclearcharge (+9)the first ionizationof stabilityof F ishigher thanthat of O. Further, theeffectof increasednuclearcharge outweightseffectof stabilitydueto exactlyhalf -filledorbitalsthereforethe `Delta_(i) H` of N and Oare lowerthan thatof F.