Which of the following sets of elements has the same valency?
- (a)Na, Mg, Ca
- (b)Na, Mg, Al
- (c)Mg, Ca, K
- (d)Mg, Ca, Ba
Correct — D, Mg, Ca, Ba. Magnesium, calcium and barium are all Group 2 (alkaline earth) metals, each with two electrons in the outermost shell, so all three have a valency of 2. Every other option mixes valencies — sodium and potassium are valency 1 and aluminium is valency 3 — so only set (d) shares a single common valency.
- (a)Na, Mg, Ca — Sodium has valency 1 while magnesium and calcium have valency 2 — not all the same.
- (b)Na, Mg, Al — Three different valencies here — sodium (1), magnesium (2) and aluminium (3).
- (c)Mg, Ca, K — Magnesium and calcium are valency 2 but potassium is valency 1 — a mixed set.
Valency is the combining capacity of an element, set by the number of electrons it gains, loses or shares. Elements have the same number of valence electrons and hence the same valency: Group 1 (Na, K) is 1, Group 2 (Mg, Ca, Ba) is 2, and Group 13 (Al) is 3.
Sort each symbol by its group — alkali metals (Na, K) are valency 1, alkaline earth metals (Mg, Ca, Ba) are valency 2, and aluminium is 3. The only set with one common value is the all-Group-2 option.
- Mg, Ca and Ba are Group 2 (alkaline earth) metals, all with valency 2.
- Na and K are Group 1 (alkali) metals with valency 1.
- Aluminium (Al) is a Group 13 element with valency 3.
- Elements of the same group share the same valency because they have the same number of valence electrons.
Only Mg, Ca and Ba share one valency (2); every other option mixes valency 1, 2 or 3.
- Assuming metals in the same option share a valency without checking their groups.
- Forgetting that aluminium is valency 3, not 2.
Asked as 'which set has the same valency' — assign each element its group and valency, then find the set that is uniform.
No directly related past PYQ was found.
- practice — not a real PYQ
The valency of calcium (Ca) is
- (a)1
- (b)2
- (c)3
- (d)4
Answer(b) 2 — calcium is a Group 2 alkaline earth metal.
- practice — not a real PYQ
Which one of the following elements has a valency of 3?
- (a)Sodium
- (b)Magnesium
- (c)Aluminium
- (d)Potassium
Answer(c) Aluminium — a Group 13 element.