Given below are two statements: Statement I: The second ionisation enthalpy of Na is larger than the corresponding ionisation enthalpy of Mg. Statement II: The ionic radius of \(\mathrm{O}^{2-}\) is larger than that of \(\mathrm{F}^{-}\). 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 false but statement II is true

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

JEE Main · 2026 · 23 Jan 2026 · Shift 2 · Classification of Elements and Periodicity

Given below are two statements:

Statement I: The second ionisation enthalpy of Na is larger than the corresponding ionisation enthalpy of Mg.

Statement II: The ionic radius of

O^{2 -}

is larger than that of

F^{-}

.

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✓ Correct
(B)Both statement I and statement II are false
(C)Statement I is false but statement II is true
(D)Statement I is true but statement II is false

Answer: (A)

Solution

The second ionisation of sodium removes an electron from the stable neon-like

N a^{+}

core, whereas that of magnesium removes the loosely held

3 s

electron of

M g^{+}

; the former costs far more energy, so the second ionisation enthalpy of Na exceeds that of Mg. For the isoelectronic anions

O^{2 -}

and

F^{-}

(ten electrons each), the smaller nuclear charge of oxygen (

Z = 8

versus

9

) holds the cloud less tightly, so

O^{2 -}

is larger than

F^{-}

. Both statements are true.

JEE Main · 2026 · 23 Jan 2026 · Shift 2 · Single correct option

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

JEE Main · 2026 · 23 Jan 2026 · Shift 2 · Classification of Elements and Periodicity

Solution

More JEE Main questions on Classification of Elements and Periodicity