If the first ionisation enthalpy of Li,Be,and | vedclass

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(C) The first ionisation enthalpy values for $Li$,$Be$,and $C$ are $520$,$899$,and $1086 \ kJ \ mol^{-1}$ respectively.Ionisation enthalpy generally i

Vedclass · Accepted Answer

$801$

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(C) The first ionisation enthalpy values for $Li$,$Be$,and $C$ are $520$,$899$,and $1086 \ kJ \ mol^{-1}$ respectively.Ionisation enthalpy generally increases from left to right across a period due to an increase in effective nuclear charge and a decrease in atomic size.The electronic configurations are:$Li: [He] \ 2s^1$$Be: [He] \ 2s^2$$B: [He] \ 2s^2 \ 2p^1$$C: [He] \ 2s^2 \ 2p^2$Due to the stable fully-filled $2s$ orbital in $Be$,its ionisation enthalpy is higher than that of $B$,which has a single electron in the $2p$ orbital.Therefore,the trend in ionisation enthalpy for these elements is $C > Be > B > Li$.Substituting the given values: $1086 > 899 > B > 520$.The value for $B$ must be between $520$ and $899 \ kJ \ mol^{-1}$.Among the given options,$801 \ kJ \ mol^{-1}$ is the only value that fits this range.Thus,the correct option is $(C)$.

If the first ionisation enthalpy of $Li$,$Be$,and $C$ respectively are $520$,$899$,and $1086 \ kJ \ mol^{-1}$,the first ionisation enthalpy (in $kJ \ mol^{-1}$) of $B$ will be:

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