Consider the following diverse set of representative elements: and . Exactly how many of these eleme — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

Elements with exceptionally stable configurations resist the addition of an electron, resulting in a positive $\Delta_{eg}H$. Noble gases ($He, Ne, Ar$) have completely filled $ns^2 np^6$ shells. Alkaline earth metals ($Be, Mg$) have completely filled $ns^2$ subshells. Nitrogen ($N$) has a highly stable, exactly half-filled $2p^3$ subshell. Therefore, all 6 of the listed elements have a positive first electron gain enthalpy.