JEE Main · 2026 · 22 Jan 2026 · Shift 2 · Classification of Elements and Periodicity

Along the second period the first ionization enthalpy rises with nuclear charge but dips at oxygen, whose $2p^4$ configuration lacks the half-filled stability that nitrogen's $2p^3$ enjoys, so the order $\mathrm{C}<\mathrm{O}<\mathrm{N}<\mathrm{F}$ holds and Statement-I is true. Within group 16 the magnitude of the electron gain enthalpy is greatest for sulphur and then decreases down the group through selenium, tellurium and polonium, while oxygen, being very small, suffers strong inter-electronic repulsion and has the smallest magnitude, giving $\mathrm{S}>\mathrm{Se}>\mathrm{Te}>\mathrm{Po}>\mathrm{O}$, so Statement-II is also true. Both Statement-I and Statement-II are true.