NDA (II) 2024 GAT Q59: Which of the following anions has a valency of

Q: What is the answer to NDA (II) 2024 GAT Q59?

A. Correct — A, Nitride. Nitrogen sits in group 15 and completes its octet by gaining three electrons, forming the nitride ion N3-. Three extra electrons means three units of negative charge, so the valency of the nitride ion is -3 — the only option that fits. (Provisional — pending the official UPSC key.)

NDA (II) 2024 General Ability Test · Question 59 of 141

Question text verified against the official NDA question paper.

Provisional answers. UPSC has not yet released the official NDA 2024 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.

Which of the following anions has a valency of -3?

(a)Nitride
(b)Nitrate
(c)Sulphide
(d)Sulphate

Answer

Why

Correct — A, Nitride. Nitrogen sits in group 15 and completes its octet by gaining three electrons, forming the nitride ion N3-. Three extra electrons means three units of negative charge, so the valency of the nitride ion is -3 — the only option that fits.

Why the others are wrong

(b)Nitrate — Nitrate is the oxoanion NO3- and carries only a single negative charge, so its valency is -1, not -3.
(c)Sulphide — Sulphur (group 16) gains two electrons to form the sulphide ion S2-, giving a valency of -2.
(d)Sulphate — Sulphate is the oxoanion SO4^2- with a charge of -2, so its valency is -2, not -3.

Concept

The valency of an ion equals the magnitude of the charge it carries. A monatomic anion gains as many electrons as it needs to reach a noble-gas configuration: nitrogen gains 3 (N3-), oxygen and sulphur gain 2 (O2-, S2-), the halogens gain 1 (Cl-). Oxoanions carry a net charge set by the whole group — nitrate NO3- is -1 and sulphate SO4^2- is -2.

Watch the naming clue: an '-ide' ending marks a simple anion of the element (nitride N3-, sulphide S2-), while an '-ate' ending marks an oxygen-containing oxoanion (nitrate NO3-, sulphate SO4^2-). Only nitrogen's simple anion reaches -3, so nitride is the answer.

Key facts

Nitride ion N3- has a valency of 3 (charge -3).
Nitrate NO3- is -1; sulphide S2- is -2; sulphate SO4^2- is -2.
'-ide' names simple anions; '-ate' names oxygen-containing (oxo) anions.
Valency of a monatomic ion = number of electrons gained or lost.

Anion → charge (valency)

Nitride (N3-)→valency -3

Nitrate (NO3-)→valency -1

Sulphide (S2-)→valency -2

Sulphate (SO4 2-)→valency -2

Only the nitride ion carries three negative charges, so its valency is -3.

Study next

Writing chemical formulae by the criss-cross (valency) methodCommon cations and anions with their chargesDifference between valency and oxidation numberNaming rules: -ide, -ate and -ite endings

Common traps

Confusing nitride (N3-, valency -3) with nitrate (NO3-, valency -1).
Assuming sulphide and sulphate have different charges — both are -2, though they are different species.

Asked as 'which ion has valency X', or embedded in formula-writing questions.

Related PYQs

No directly related past PYQ was found.

Practice

practice — not a real PYQ
The valency of the sulphate ion (SO4^2-) is:
- (a)1
- (b)2
- (c)3
- (d)4
Answer(b) 2 — the sulphate oxoanion carries a net charge of -2.
practice — not a real PYQ
Which pair of anions both carry a valency of -1?
- (a)Chloride and nitrate
- (b)Oxide and sulphide
- (c)Nitride and phosphide
- (d)Carbonate and sulphate
Answer(a) Chloride and nitrate — Cl- and NO3- are both single-negative anions.