An unknown main-group element has the following successive ionization enthalpies recorded in : , , . — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

There is a massive, sudden jump between the first and second ionization enthalpies ($520 \text{ kJ/mol}$ vs $7300 \text{ kJ/mol}$). This extreme spike indicates that after losing one electron, the resulting ion achieves a highly stable, completely filled noble gas core. Thus, the neutral element must have exactly 1 valence electron (an Alkali metal).