Generallythe firstionizationenergyincreases along aperiod.Butthere aresome exceptions. One whichis not anexception is

Generallythe firstionizationenergyincreases along aperiod.Butthere are

1.	Generallythe firstionizationenergyincreases along aperiod.Butthere aresome exceptions. One whichis not anexception is
Answer» N andO NA andMg Mg and A1 Be and B Solution :Inspiteof highernuclearchargethe ionizationenthalpyof O islowerthan thatof Nbecause Nhas exactlyhalf- filledmorestableelectronicconfigurationbut Odoesnot. Similarlyin spiteof highernuclearcharge, ionizationenthalpyofA1 islowerthan thatof Mgbecausein case of A1a lessstronglyattracted 3p- ELECTRONIS to beremoved3s- ELECTRON is to beremoved. Likewise, in SPITE of highernuclearcharge , the ionizationenthalpyof B islower than thatof Bebecausein caseof B , alessstronglyheld 2P- electron is to beremovedwhile incase of Mga morestronglyheld2s- electron isto beremoved. Howeverin case of Naand Mgionizationenthalpyincreasesas teh nuclearchargeincreases. Thereforeoption (b ) is correct.