The successive ionization potentials of an element are measured as , and . What is the exact number — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

There is a massive, sudden jump in ionization energy between $IE_3$ ($37.9 \text{ eV}$) and $IE_4$ ($259.3 \text{ eV}$). This indicates that the 4th electron is being removed from a stable, fully-filled inner noble gas core. Therefore, element $M$ has exactly 3 valence electrons (Group 13 element). Its stable oxidation state is $+3$, so it will form a trihalide with the formula $MX_3$.