Given below are two statements : Statement (I): The first ionisation enthalpy of the elements $\mathrm{Na}, \mathrm{Mg}, \mathrm{Cl}$ and Ar follows the order $\mathrm{Na}>\mathrm{Mg}>\mathrm{Cl}>\mathrm{Ar}$ Statement (II) : Among $\mathrm{Ca}, \mathrm{Al}, \mathrm{Fe}$ 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 :

(D) Statement I is false but Statement II is true

(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

JEE Main · 2026 · 02 Apr 2026 · Shift 1 · Classification of Elements and Periodicity

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✓ Correct

Answer: (D)

Solution

Across a period the first ionisation enthalpy rises, so the true order is

Na < Mg < Cl < Ar

; the sequence given reverses this and is false. Calcium has the configuration

[Ar] 4 s^{2}

, so after losing two electrons

C a^{2 +}

reaches the stable argon core; removing a third electron from this noble-gas core demands exceptionally high energy, much greater than the third ionisation of B, Al or Fe, so that statement is true.

JEE Main · 2026 · 02 Apr 2026 · Shift 1 · Single correct option

Practise more: all JEE Main PYQs on Classification of Elements and Periodicity →

JEE Main · 2026 · 02 Apr 2026 · Shift 1 · Classification of Elements and Periodicity

Solution

More JEE Main questions on Classification of Elements and Periodicity