Four elements A ,B ,C and Dalongwith theirelectonic configurationare givenbelow : Elements:ABCD Electronic configuration :2,12,82,8,12,8,8 Nowanswerthe followingquestions : (i)Which two elements belongto thesameperiod ? (ii)Which two elements belongto thesamegroup ? (iii) Whichtwo elements belongto the 18thgroup ? (iv) Which element out of Aand C ismorereactiveand why ? (v) Whichelementout of Aand B formsthemaximumnumber tocompounds ?

Four elements A ,B ,C and Dalongwith theirelectonic configurationare g

1.	Four elements A ,B ,C and Dalongwith theirelectonic configurationare givenbelow : Elements:ABCD Electronic configuration :2,12,82,8,12,8,8 Nowanswerthe followingquestions : (i)Which two elements belongto thesameperiod ? (ii)Which two elements belongto thesamegroup ? (iii) Whichtwo elements belongto the 18thgroup ? (iv) Which element out of Aand C ismorereactiveand why ? (v) Whichelementout of Aand B formsthemaximumnumber tocompounds ?
Answer» Solution :(i) Elementsin aperiodhave samenumberof shells . Thuselements A and Beach withtwo shellsbelongto secondperiod whileelements C and Dwhichhavethreeshells each belongto thirdperiod. (ii)elements in a grouphavesamenumber of valenceelectrons. thuselements A and Cbelongto THESAME group . (iii) Elementshaving all shellscompletely filledbelongto group 18 (noblegases. ) ThuselementsB and Dbelongto 18thgroup . (iv) BECAUSEOF biggersizeand weakerforcesof attraction of thenucleus on thevalenceelectronelementC (2,8,1)is morereactivethanelement A. (V) Bbeinga noblegas doesnot formcompounds . Butelement Ahas onlyelectronin thevalenceshellwhich ITCAN loseveryeasily. therefore, ELEMENT A formsmaximumnumberof compounds.