JEE Advanced 2026 · Paper 2 · Chemistry Q7

ChemistryMultiple correct+4 / -1Question 43 of 54

The correct statement(s) regarding the periodic properties of elements is(are)

Second ionization enthalpy of carbon atom is less than that of boron atom.

Increasing order of ionic radii:

\ce{Al^3+}<\ce{Mg^2+}<\ce{Na+}

Under identical conditions, in solid state, the density of potassium metal is more than density of sodium metal.

The H-H bond is weaker than F-F bond.

Answer and worked solution

Official answer: A, B

(A) The second electron of C comes from $\ce{C+}$ ( $2s^22p^1$ ), a 2p electron. That of B comes from $\ce{B+}$ ( $2s^2$ ), a more penetrating 2s electron from a filled subshell. Values: about 2353 kJ/mol for C and 2427 kJ/mol for B. True.
(B) These ions are isoelectronic (10 electrons), so the radius falls as nuclear charge rises: $\ce{Al^3+}<\ce{Mg^2+}<\ce{Na+}$ . True.
(C) K (0.86 g cm⁻³) is less dense than Na (0.97 g cm⁻³), an anomaly due to K's much larger atomic volume. False.
(D) H-H (436 kJ/mol) is far stronger than F-F (158 kJ/mol, weakened by lone-pair repulsion). False.

JEE Advanced 2026 · Paper 2, Chemistry question 7