In graphite, each carbon atom is bonded to three other carbon atoms
- A.forming a three-dimensional structure
- B.in the same plane giving a hexagonal array
- C.in the same plane giving a square array
- D.in the same plane giving a pentagonal array
Correct answer
Explanation
The correct answer is B, in the same plane giving a hexagonal array. In graphite each carbon atom is joined to three others in a flat layer of hexagonal rings, like a honeycomb. Each carbon has four valence electrons; three form strong covalent bonds within the layer, and the fourth is free to move across the layer. These free electrons make graphite a good conductor of electricity, unlike most non-metals, which is why it is used for electrodes. The layers are held together only by weak van der Waals forces, so they slide over one another easily. That makes graphite soft and slippery, useful as a dry lubricant and in pencil "lead". A single such layer is called graphene. Option A is wrong because a three-dimensional network, with each carbon bonded to four others, is the structure of diamond. Option C is wrong because the carbon atoms in graphite do not form square rings. Option D is wrong because graphite layers are made of six-membered rings, not five-membered ones. Exam tip: diamond, four bonds, 3D tetrahedral, hard insulator; graphite, three bonds, flat hexagons, soft conductor.
Practice Questions
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- A.Thomas Savery
- B.Thomas Newcomen
- C.James Watt
- D.Richard Arkwright
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- A.20 Ω
- B.10 Ω
- C.5 Ω
- D.15 Ω
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- A.nearby object is focused beyond the retina.
- B.nearby object is focused before the retina.
- C.distant object is focused before the retina.
- D.distant object is focused beyond the retina.
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Read the full explanation →A homogeneous mixture contains two liquids. How are they separated ?
- A.By filtration
- B.By evaporation
- C.By distillation
- D.By condensation
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Read the full explanation →Cartilage is NOT found in
- A.larynx
- B.nose
- C.ear
- D.urinary bladder
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