JEE Main 2026 — Apr 2, Shift 1 — Chemistry solution

JEE Main2026Apr 2, Shift 1Chemistry

Given below are two statements :

Statement (I) : The first ionisation enthalpy of the elements Na, Mg, Cl and Ar follows the order Na $>$ Mg $>$ Cl $>$ Ar

Statement (II) : Among Ca, Al, Fe and B, the third ionisation enthalpy is very high for Ca.

In the light of the above statements, choose the correct answer from the options given below :

A
Both Statement I and Statement II are true
B
Both Statement I and Statement II are false
C
Statement I is true but Statement II is false
D
Statement I is false but Statement II is true

Solution

The correct first ionisation enthalpy order across the third period is Na $<$ Mg $<$ Cl $<$ Ar (it generally increases left to right, with Ar being a noble gas at maximum). The order given in Statement I is exactly reversed, so Statement I is false.

Calcium has the electron configuration [Ar] $4 s^{2}$ . After removing two valence electrons, $C a^{2 +}$ attains the stable noble-gas configuration of Ar. Removing a third electron requires breaking into this closed shell, making the third ionisation enthalpy exceptionally high compared with Al, Fe and B. Statement II is true.

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