JEE Main 2026 · 2 Apr · Shift 1 · Chemistry Q59

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ChemistrySingle correct+4 / -1Question 59 of 75

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 :

Both Statement I and Statement II are true

Both Statement I and Statement II are false

Statement I is true but Statement II is false

Statement I is false but Statement II is true

Answer and worked solution

Official answer: D

Statement I. Across period 3, first ionisation enthalpy rises: Ar > Cl > Mg > Na. The stated order is the reverse: false.

Statement II. Removing a third electron from Ca breaks into the stable $[\ce{Ar}]$ core ( $\ce{Ca^{2+}}$ is noble-gas-like), so $IE_3$ of Ca is very high: true. (Al and B lose a valence electron third; Fe goes from $3d^6$ to $3d^5$ .)

(D)

Topics:Ionisation enthalpy

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JEE Main 2026 · 2 Apr · Shift 1, Chemistry question 59