JEE Main 2026 Jan 23 Shift 1, Chemistry Q3: Periodicity In Atomic Properties

JEE Main2026Jan 23, Shift 1Chemistry

The correct trend in the first ionization enthalpies of the elements in the 3 $^{rd}$ period of periodic table is:

A
Al $<$ Si $<$ S $<$ P $<$ Cl
B
Al $<$ S $<$ P $<$ Si $<$ Cl
C
Si $<$ S $<$ Al $<$ P $<$ Cl
D
S $<$ Si $<$ Al $<$ P $<$ Cl

Solution

Across the third period, first ionization enthalpy generally rises with $Z_{eff}$ . The one anomaly is the dip at S vs P: phosphorus has a half-filled $3 p^{3}$ configuration that is extra stable, so removing an electron from P needs more energy than from S.

$∴$ Al $<$ Si $<$ S $<$ P $<$ Cl.

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JEE Main 2026 Jan 23 Shift 1, Chemistry Q3: Periodicity In Atomic Properties

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