Topic: Ionization enthalpy and electron gain enthalpy· Classification of Elements and Periodicity in Properties

Arrange the following elements in increasing order of first ionization enthalpy:Li, Be, B, C, NChoose the correct answer from the options given below:

1. Li < Be < N < B < C

2. Li < Be < B < C < N

3. Li < B < Be < C < N

4. Li < Be < C < B < N

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Answer: 3. Li < B < Be < C < N

Key idea: ionization enthalpy increases across a period, with exceptions at Be (filled 2s) and N (half-filled 2p).

Be (\(2s^2\)) is more stable than B (\(2s^22p^1\)), so IE of B is lower than Be. N (\(2s^22p^3\)) has a half-filled 2p subshell, so its IE is the highest of the five.

Order: \(\mathrm{Li < B < Be < C < N}\) (520, 801, 899, 1086, 1402 kJ/mol). Option 3.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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Arrange the following elements in increasing order of first ionization enthalpy:Li, Be, B, C, NChoose the correct answer from the options given below:

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