Assertion : The covalency of carbon is four in excited state.
Reason : The four half-filled pure orbitals of carbon form same kind of bonds with an atom as those are with hybridised orbitals.

Options

A. If assertion is true but the reason is false
B. If assertion is false but reason is true
C. IF both assertion and reason are true and the reason is the correct explanation of assertion
D. If both assertion and reason are true but reason is not the correct explanation of assertion

Answer

To solve the problem, we need to analyze both the assertion and the reason provided in the question.

### Step 1: Understand the Assertion
The assertion states that "The covalency of carbon is four in excited state."

- Covalency refers to the maximum number of bonds an atom can form.
- Carbon has an atomic number of 6, with an electron configuration of 1s² 2s² 2p² in its ground state.
- In the excited state, one of the 2s electrons can be promoted to the 2p orbital, resulting in the configuration 1s² 2s¹ 2p³.
- This gives carbon four half-filled orbitals (one 2s and three 2p), allowing it to form four covalent bonds.

**Conclusion for Step 1**: The assertion is true.

### Step 2: Understand the Reason
The reason states that "The four half-filled pure orbitals of carbon form the same kind of bonds with an atom as those are with hybridized orbitals."

- Hybridization involves mixing atomic orbitals to form new hybrid orbitals that can form bonds.
- In the case of carbon, when it undergoes hybridization (like sp³ hybridization), it forms four equivalent bonds.
- However, the assertion claims that the four half-filled pure orbitals form the same kind of bonds, which is misleading. The bonds formed by pure atomic orbitals (2s and 2p) are not equivalent in nature; they involve different types of overlaps (s-p and p-p).

**Conclusion for Step 2**: The reason is false.

### Step 3: Final Evaluation
Based on the analysis:
- The assertion is true: Carbon can indeed have a covalency of four in the excited state.
- The reason is false: The bonds formed by the pure orbitals are not all the same.

### Final Answer
The correct option is that the assertion is true, but the reason is false.