How doatomic radiivaryin a period andin agroup ? How doyou explain the

1.	How doatomic radiivaryin a period andin agroup ? How doyou explain thevariation ?
Answer» SOLUTION :Withina group , the atomicradiusincreasesdown the group. Thisis because a newenergyshell (i.e., principal quantum numberincreasesby unity) is ADDED at each succeedingelementwhile thenumber OFELECTRONS in THEVALENCE shellremainsto be thesame. In otherwordsthe ELECTRONSIN thevalenceshell ofeachsucceedingelementliefartherand farther awayfrom thenucleus.As a resultthe force ofattraction of the nucleus for thevalenceelectronsdecreases andhencetheatomicsizeincreases. In contrast the atomicsize decreasesas wemovefrom leftto rightin a period. Thisis because thatwithin a period the outherelectrons remain in the sameshell but thenuclearchargeincreasesby oneunitat eachsucceedingelement . Dueto thisincreased nuclearcharge , the attraction of the numberfor theouther electrons increases and hencethe atomicsizedecreases.

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