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Arrangethe elementsof secondperiodin orderof increasingsecondionizationenthalpies. |
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Answer» Solution :The electron CONFIGURATION of the ionsobtainedafterremovalof firstelectronfrom theelements of2nd `(1s^(2) 2s^(2)2p^(3), F^(+) (1s^(2) 2s^(2) 2p^(4))` and `(Ne^(+) (1s^(2) 2s^(2) 2p^(5))` Thefollowingconclusions can bedrawnfrom theaboveconfiguration (i) `Li^(+)` has nolegas VIZ. He gasconfigurationtherefore`Delta_(i)H_(2)`of Li is thehighest in the secondperiod (ii) Since `B^(+)` the electronhas to beremovalfrom amorestablefullyfilled2 s-orbitalwhilein `Be^(+)` ithas to belost fromthe lessstablehalf-filled 2s-orbitalandfurthermore, the lossof anelectronfrom `Be^(+)` givesmore stable `Be^(2+)` ion withnoblegas configuration therefore `Delta_(i)H_(2)` of Be islowerthan thatof B. (iii)Sincemoreenergy is requiredto remove an s-electron than a p-electronof thesameenergy level thereforemore energy is requiredto removea 2s-electronfrom `B^(+) (1s^(2) 2s^(2))` than a 2p- electronfrom`C^(+) (1s^(2) 2s^(2) 2p^(1))`. Inotherwords `Delta_(i)H_(2)` of Cis lowerthan that of B. (iv) As wemovefrom C to N O, thenuclear charge increases by oneunit attimethereforetheir`Deltai H_(2)` alsoincreaseaccordingly. Inotherwords `Delta_(i)H_(2)` ofhighest thanthat of N whichin turnis higher thanthat of C. (v) In caseof `O^(+) (1s^(2)2s^(2) 2p^(3))` and electronis to befrom an exactlyhalf- filled2p- orbitalbut in case of`F^(+) (1s^(2) 2s^(2) 2p^(4))` THISIS notso. However, lossof an electron from `F^(+)` givesan exactlyhalf-filled2p- ORBITAL(i.e, `F^(2+) (1s^(2) 2s^(2) 2p^(3))` therefore `Delta_(i)H_(2)` of F shouldbe lowerthan thatof O. (vi)Like `O^(+) (1s^(2) s^(2) 2p^(3))` and `F^(+) (1s^(2)2s^(2)2p^(4))` in caseof `Ne^(+) (1s^(2) 2s^(2)2p^(5))` alsoan electronis to beremovedfrom a 2p-orbital. SinceNe hasthehighestnuclear nuclearchargein 2ndperiod`Delta_(i)H_(2)` ofNe isexpectedto bemuchhigherthan thatof O ro E. Fromthe abovediscussionit follows that `Delta_(i)H_(2)` of THEELEMENTSOF 2ndperiodincreasein the order. `Be lt C lt B lt N lt F ltO ltNe ltLi` |
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