For the second period elements the correct increasing order of first ionisation enthalpy is :

1. Li < Be < B < C < N < O < F < Ne

2. Li < B < Be < C < O < N < F < Ne

3. Li < B < Be < C < N < O < F < Ne

4. Li < Be < B < C < O < N < F < Ne

Doubtly Asked 30 Oct 2026 NEET UG 2019 Practice test neet Save WhatsApp Report

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Answer: 2. Li < B < Be < C < O < N < F < Ne

First ionisation enthalpy generally increases across a period, with two exceptions in period 2.

Order: Li < B < Be < C < O < N < F < Ne, option (2).

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

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