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# Which is the correct order of second ionisation energy ?

$\begin{array}{1 1} Si < S < P < Cl \\ Si < P < S < Cl \\ P < Si < Cl > S \\ Si < P < Cl < S \end{array}$

$Si^{+} -2p^1$
$P^{+} -2p^2$
$S^{+} -2p^3$
$Cl^{+} -2p^4$
Clearly $S^+$ has half filled orbital.