Match List-I with List-II and select the correct answer using the code given below the Lists: List-I (Allotrope of Carbon) A. Graphite B. Diamond C. Fullerene D. Graphene List-II (Property) 1. Thinnest and strongest material 2. Hardest natural substance 3. Very light and strong material 4. Soft and slippery material Code:
- (a)A-4, B-2, C-3, D-1
- (b)A-4, B-3, C-2, D-1
- (c)A-1, B-3, C-2, D-4
- (d)A-1, B-2, C-3, D-4
Correct — A, the pairing A-4, B-2, C-3, D-1. Graphite (A) has a layered structure whose sheets slide over one another, making it soft and slippery (4) and useful in pencils and as a lubricant. Diamond (B) has a rigid three-dimensional network of carbon atoms, which makes it the hardest natural substance (2). Fullerenes (C) such as C60 are hollow cage-like molecules that are very light and strong (3). Graphene (D) is a single one-atom-thick sheet of carbon and is the thinnest yet strongest material tested (1). These four correct pairings give option A.
- (b)A-4, B-3, C-2, D-1 — It swaps diamond and fullerene: it calls diamond 'light and strong' and fullerene the 'hardest', whereas diamond is the hardest natural substance and fullerenes are the light, strong cage molecules.
- (c)A-1, B-3, C-2, D-4 — It reverses graphite and graphene, labelling graphite the 'thinnest and strongest' and graphene 'soft and slippery' — but graphene is the one-atom-thick strong sheet, while graphite is the soft, layered solid.
- (d)A-1, B-2, C-3, D-4 — Diamond and fullerene are placed correctly, but graphite is wrongly called 'thinnest and strongest' and graphene 'soft and slippery'; those two labels belong the other way round.
Allotropes are different structural forms of the same element. Carbon's allotropes share only the carbon atom but differ completely in how the atoms are bonded, which gives each one very different properties: diamond (3-D network), graphite (stacked sheets), fullerenes (closed cages such as C60), graphene (a single sheet) and carbon nanotubes (rolled sheets).
Match each form to what its structure implies. A rigid 3-D network resists deformation, so diamond is hardest. Loosely held layers slide, so graphite is soft and slippery. A single sheet only one atom thick is extraordinarily thin yet strong, so graphene tops the list. Hollow molecular cages are light but sturdy, so fullerenes are light and strong. Working from structure to property avoids memorising the table blindly.
- Diamond is the hardest known natural substance because every carbon is bonded to four others in a rigid tetrahedral network.
- Graphite conducts electricity and acts as a lubricant because its layers are weakly held and can slide.
- Graphene is a single one-atom-thick layer of carbon and is among the thinnest yet strongest materials known.
- Fullerenes such as C60 (buckminsterfullerene) are hollow, cage-like carbon molecules.
The correct pairing is A-4, B-2, C-3, D-1 (option A).
- Swapping graphite and graphene — graphene is the strong single sheet, graphite is the soft layered solid.
- Calling fullerene the hardest form; diamond is the hardest.
- Assuming all carbon forms behave alike when their properties are opposite.
NDA and other exams give a match-the-following of carbon allotropes with properties or uses — link each property back to the allotrope's structure.
Graphene is frequently in news recently. What is its importance? 1. It is a two-dimensional material and has good electrical conductivity. 2. It is one of the thinnest but strongest materials tested so far. 3. It is entirely made of silicon and has high optical transparency. 4. It can be used as conducting electrodes required for touch screens, LCDs and organic LEDs. Which of the statements given above are correct?
- (a) 1 and 2 only
- (b) 3 and 4 only
- (c) 1, 2 and 4 only
- (d) 1, 2, 3 and 4
Answer(c) 1, 2 and 4 only
Same allotrope — graphene. This UPSC question confirms that graphene is a two-dimensional carbon sheet and among the thinnest yet strongest materials, exactly the property matched to graphene here.
- practice — not a real PYQ
Which allotrope of carbon is used as a lubricant and in pencils because of its soft, layered structure?
- (a)Diamond
- (b)Graphite
- (c)Fullerene
- (d)Graphene
Answer(b) Graphite — its weakly bonded layers slide over one another, making it soft, slippery and useful as a lubricant.
- practice — not a real PYQ
Buckminsterfullerene (C60) is best described as
- (a)a rigid three-dimensional network of carbon
- (b)a single one-atom-thick sheet of carbon
- (c)a hollow cage-like molecule of carbon
- (d)an amorphous form of carbon
Answer(c) a hollow cage-like molecule of carbon — C60 is a closed cage of 60 carbon atoms shaped like a football.