Theincreasingorder orreactivity amonggroup 1 element is Li lt Na lt K lt Rb lt Cs whereasthe of group17isF gt C1 gt Br gt I. Explain.

Theincreasingorder orreactivity amonggroup 1 element is Li lt Na lt K

1.	Theincreasingorder orreactivity amonggroup 1 element is Li lt Na lt K lt Rb lt Cs whereasthe of group17isF gt C1 gt Br gt I. Explain.
Answer» Solution :Theelements of group1 haveonly oneelectronin theirrespectivevalenceshellsand thusa strong tendencyto losethiselectron. Thetendencyto loseelectrons in turn DEPENDS upon theionizationenthalpy. Sincethe ionizationenthalpydecreasesdownthe groupthereforethe reactivityof group1 elements increasesin the sameorder : `LI lt Na lt K lt Rb ltCs.` In contrastthe elements of group17 haveseven electrons in theirrespectivevalenceshellsand thushave astrong tendencyto accept one moreelectron Thetendency to accept electronsin turn dependsupontheirelectrode potentials.Sincetheelectrode potentialsof group17 elements decreasesin the order : `F (+ 2.87 V ) GT C1 ( + 1.36 V ) , Br ( 1.08 V )` and `I (+ 0.53 V)` thereforetheirreactivitiesalso decreases in the sameorder `: F gt C1 gt Br gt I` Alternativelytendency toaccept electrons can belinked to electrongain enthalpy. sinceelectrongainenthalpybecomesless and lessnegativeas we move fromC1 to I thereforereactivityincreasesfromto I, F ,howeveris themostreactive due toits lowbonddissociationenergy .