SSC CGL 2024 Tier-I · 10 September 2024, Shift 3 · General Awareness · Question 20 of 100

Text as printed on a candidate's response sheet for this shift; answer per SSC's tentative key as marked on that sheet. Solution last reviewed 6 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. The questions and options here are reproduced as printed on a candidate's own response sheet for this shift — the Commission's text, unchanged. Each answer is SSC's tentative key as marked on that sheet; SSC allowed challenges to it and never publishes a final key. The solutions are written by UnlockIAS.

Which of the following elements is a metalloid?

(a)Sodium
(b)Iron
(c)Silicon
(d)Oxygen

Answer

Why

Correct — C. Silicon sits on the stepped diagonal line of the periodic table that separates metals from non-metals, and that is exactly what a metalloid is - an element with properties of both.

It has a metallic lustre but is brittle rather than malleable, and it conducts far worse than a metal and far better than a non-metal.

That intermediate conductivity - the definition of a semiconductor - is why silicon carries the chip industry.

Why the others are wrong

(a)
Sodium — Sodium is an alkali metal from Group 1: soft, highly reactive and a good conductor. Nothing about it is intermediate.
(b)
Iron — Iron is a transition metal - malleable, ductile and strongly conducting. It passes every test that separates a metal from a metalloid.
(d)
Oxygen — Oxygen is a non-metal, a gas at room temperature and a poor conductor. That is the far side of the dividing line, not the middle of it.

Concept

Elements are sorted into metals, non-metals and metalloids.

Metals are lustrous, malleable, ductile and conduct heat and electricity. Non-metals are usually dull, brittle when solid, and poor conductors.

Metalloids lie along the staircase between the two blocks and borrow from each side. The list to memorise is short and stable: boron, silicon, germanium, arsenic, antimony and tellurium.

Their intermediate conductivity, tunable by adding impurities, is what makes semiconductor electronics possible.

Key facts

The commonly listed metalloids are boron, silicon, germanium, arsenic, antimony and tellurium.
Metalloids lie along the stepped diagonal line that separates metals from non-metals in the periodic table.
Silicon is a semiconductor, which is why it is the base material of integrated circuits and solar cells.
Silicon is the second most abundant element in the Earth's crust, after oxygen.

Study next

Physical properties that separate metals, non-metals and metalloidsSemiconductors, doping, and how they differ from conductors and insulatorsPeriodic table blocks and the position of the metalloid staircase

Common traps

Reading metalloid as metal-like and picking a shiny metal such as iron.
Letting abundance decide the answer - oxygen is the most abundant element in the crust and is still a non-metal.

This classification question has one shape: which of four listed elements is a metalloid, a noble gas or a halogen. The list to hold is short.

Another chemistry item in this shift, 10 Sep 2024, 16:00, GA Q.8, asks what causes a redox reaction.

Related PYQs

No directly related past PYQ was found.