NDA (I) 2025 GAT Q75: Element X forms a chloride with the formula XCl2, which is

Q: What is the answer to NDA (I) 2025 GAT Q75?

C. Correct — C, Mg. A chloride of formula XCl2 means X combines with two chlorine atoms, so X is divalent — its valency is 2. A high-melting-point solid chloride points to an ionic metal chloride. Magnesium forms MgCl2 and belongs to Group 2 (the alkaline-earth metals), so X most likely shares magnesium's group. (Provisional — pending the official UPSC key.)

NDA (I) 2025 General Ability Test · Question 75 of 150

Question text verified against the official NDA question paper.

Provisional answers. UPSC has not yet released the official NDA 2025 answer key (it is published several months after the exam). The answers here are our best-supported answers — derived from careful subject-solving and cross-checked against independent solved papers and primary sources — and will be reconciled to the official key as soon as UPSC publishes it. They are not the official UPSC answer key.

Element X forms a chloride with the formula XCl2, which is a solid with high melting point. X would most likely be in the same group of periodic table as

(a)Na
(b)Al
(c)Mg
(d)K

Answer

Why

Correct — C, Mg. A chloride of formula XCl2 means X combines with two chlorine atoms, so X is divalent — its valency is 2. A high-melting-point solid chloride points to an ionic metal chloride. Magnesium forms MgCl2 and belongs to Group 2 (the alkaline-earth metals), so X most likely shares magnesium's group.

Why the others are wrong

(a)Na — Sodium is in Group 1 and is monovalent; it forms NaCl (formula XCl, not XCl2), so it cannot be X's group.
(b)Al — Aluminium is in Group 13 and is trivalent, forming AlCl3 — that is XCl3, not XCl2.
(d)K — Potassium, like sodium, is a Group 1 monovalent metal forming KCl (XCl); it does not match the XCl2 formula.

Concept

The formula of a chloride reveals the metal's valency: XCl gives a valency of 1, XCl2 a valency of 2, and XCl3 a valency of 3. Group 2 (alkaline-earth) metals such as magnesium and calcium are the divalent ones.

Work backward from the formula. Two chlorines mean valency 2, which is the alkaline-earth signature, and only magnesium among the four options is a Group 2 metal.

Key facts

XCl2 implies a valency of 2, characteristic of Group 2 (alkaline-earth) metals.
Magnesium (MgCl2) is a Group 2 metal, as are calcium, strontium and barium.
Group 1 metals such as Na and K are monovalent (XCl); Group 13 aluminium is trivalent (XCl3).
A high-melting solid chloride indicates ionic bonding between a metal and chlorine.

What the chloride formula tells you about the group

Na, K (Group 1)→Valency 1 → chloride XCl (e.g. NaCl)

Mg (Group 2)→Valency 2 → chloride XCl2 (e.g. MgCl2)

Al (Group 13)→Valency 3 → chloride XCl3 (e.g. AlCl3)

XCl2 means valency 2 — the alkaline-earth signature — so X is in magnesium's group (c).

Study next

Valency and how it is read from a compound's formulaGroups of the periodic table and their typical valenciesAlkali metals (Group 1) versus alkaline-earth metals (Group 2)Ionic bonding and the properties of ionic solidsWriting chemical formulae by criss-crossing valencies

Common traps

Reading XCl2 as valency 1 or 3 instead of 2.
Picking a Group 1 metal (Na or K) that would give XCl, not XCl2.

Given a chloride formula, deduce the element's valency and hence its periodic-table group.

Related PYQs

No directly related past PYQ was found.

Practice

practice — not a real PYQ
An element M forms an oxide M2O3. Its valency is
- (a)1
- (b)2
- (c)3
- (d)4
Answer(c) 3 — M2O3 corresponds to a valency of 3, like aluminium.
practice — not a real PYQ
Which of the following elements is divalent (valency 2)?
- (a)Sodium
- (b)Potassium
- (c)Calcium
- (d)Aluminium
Answer(c) Calcium — a Group 2 alkaline-earth metal.