Theorderof decreasingnegativeelectrongainenthalpyof O. S, Se, is

1.	Theorderof decreasingnegativeelectrongainenthalpyof O. S, Se, is
Answer» `O GT SGT SE` `S gt O gt Se` `Se gt O gt S` `S gt Se gt O` Solution :As the size ofthe atomincreasesdown agroup ,the negativeelectron gainenthalpydecreasesfromtop to bottom . Howeverdue tosmallsize theinter- electronicrepulsionsin the Oatom areso strongthat negativeelectrongain of O is the smallestamong theelementsof group16. Thusthenegativeelectrongainenthalpy of O, Sand Sedecreasesin theorder : `S gt Se gt O,` i.e.,OPTION(d) is correct.

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