Which of the following elements has the last | vedclass

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(A) The magnetic quantum number $m$ for an $s$-orbital is always $0$.For $Na$ $(Z=11)$,the electronic configuration is $1s^{2} 2s^{2} 2p^{6} 3s^{1}$.

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$Na$

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(A) The magnetic quantum number $m$ for an $s$-orbital is always $0$.For $Na$ $(Z=11)$,the electronic configuration is $1s^{2} 2s^{2} 2p^{6} 3s^{1}$. The last electron enters the $3s$ orbital,which has $l=0$,therefore $m=0$.For $O$ $(Z=8)$,the configuration is $1s^{2} 2s^{2} 2p^{4}$. The last electron enters a $2p$ orbital $(l=1)$,where $m$ can be $-1, 0, +1$.For $Cl$ $(Z=17)$,the configuration is $1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{5}$. The last electron enters a $3p$ orbital $(l=1)$,where $m$ can be $-1, 0, +1$.For $N$ $(Z=7)$,the configuration is $1s^{2} 2s^{2} 2p^{3}$. The last electron enters a $2p$ orbital $(l=1)$,where $m$ can be $-1, 0, +1$.Thus,only $Na$ has its last electron in an $s$-orbital where $m$ is strictly $0$.

Which of the following elements has the last electron in its outermost orbit with a magnetic quantum number $m = 0$?

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