JEE Chemistry
JEEChemistryPeriodic Table & PeriodicityClass 11

I keep getting “Ionization energy” questions wrong in Periodic Table & Periodicity. What's the trap?

ignoring small dips (e.g. B<Be, O<N) caused by sub-shell stability.

The usual trap: ignoring small dips (e.g. B<Be, O<N) caused by sub-shell stability. How to avoid it: removing an electron is hardest from small, tightly-held atoms. Go back to the definition — the energy to remove the outermost electron; it rises across a period and falls down a group.

Key point

Ionization energy

Common mistake

ignoring small dips (e.g. B<Be, O<N) caused by sub-shell stability.

Memory tip

removing an electron is hardest from small, tightly-held atoms.

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