Among the following gas-phase processes, which one requires the absolute maximum amount of energy? — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

$Na^+$ has a highly stable, completely filled noble gas configuration ($1s^2 2s^2 2p^6$). Removing an electron from this deeply bound inner shell ($IE_2$ of $Na$) requires an enormous amount of energy, significantly more than breaking the valence $3s$ subshells in $Mg$ or the first ionization of $Na$.