Non-metals are generally bad conductors of electricity. However, graphite is a good conductor of electricity because it
- A.has free electrons
- B.is an allotrope of carbon
- C.is brittle
- D.forms basic oxide
Show answer
Correct answer: A. has free electrons
Explanation
The correct answer is A, it has free electrons. In graphite each carbon atom is joined to only three other carbon atoms in flat hexagonal layers, so the fourth valence electron of every atom is not used in bonding and can move freely along the layer. These mobile electrons carry current, which is why graphite is used to make electrodes and the brushes of electric motors.
Option B is wrong because being an allotrope of carbon explains nothing by itself: diamond is also an allotrope of carbon and does not conduct electricity at all, since all four of its electrons are locked in bonds. Option C is wrong because brittleness is a mechanical property and has no bearing on conduction. Option D is wrong because graphite does not form a basic oxide; carbon dioxide is acidic in nature, and oxide character is unrelated to electrical conductivity.