The correct option is Both A and R are true but R is NOT the correct explanation of A
Explanation
Graphite is a crystalline allotrope of carbon. Its physical properties, such as electrical conductivity and lubricity, are directly governed by its specific atomic arrangement and bonding nature.
Analysis of Assertion (A)
Correct. Graphite is a good conductor of electricity. Despite being a non-metal, it allows the flow of electric current, which is an exception to the general properties of non-metals.
Analysis of Reason (R)
Correct. Graphite has a two-dimensional layered structure consisting of hexagonal rings. These layers are stacked over one another and are held together by weak van der Waals forces. This weak inter-layer attraction allows the layers to slide over each other.
Justification for Both A and R are true but R is NOT the correct explanation of A
While both statements are factually true, the Reason (R) does not correctly explain the Assertion (A).
- The conductivity of graphite is caused by the electronic configuration of carbon atoms within the layers. Each carbon atom is $sp^2$ hybridized and forms covalent bonds with three other carbon atoms. The fourth valence electron of each carbon atom is free (delocalized) and mobile, enabling the conduction of electricity.
- The weak van der Waals forces mentioned in the Reason explain why graphite is soft and slippery (useful as a lubricant), but they are not the cause of its electrical conductivity.
Key Takeaway
Graphite conducts electricity due to the presence of free delocalized $\pi$-electrons (arising from $sp^2$ hybridization), whereas its softness and lubricating properties are due to the weak van der Waals forces between its layers.