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

**Step-by-Step Solution:**

1. **Understanding Covalency:**
- Covalency refers to the maximum number of bonds an atom can form. For carbon, this is typically 4 in its excited state.

2. **Ground State Configuration of Carbon:**
- The atomic number of carbon is 6, and its electron configuration is \(1s^2, 2s^2, 2p^2\).
- In the ground state, carbon has two half-filled orbitals (the two 2p electrons).

3. **Excited State Configuration of Carbon:**
- When one of the 2s electrons is excited to the 2p orbital, the configuration becomes \(1s^2, 2s^1, 2p^3\).
- In this excited state, carbon has four half-filled orbitals (one 2s and three 2p).

4. **Covalency in Excited State:**
- With four half-filled orbitals, carbon can form a maximum of four covalent bonds. Therefore, the assertion that the covalency of carbon is four in the excited state is **true**.

5. **Analyzing 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 formed with hybridized orbitals.
- In reality, the bonds formed by the 2s and 2p orbitals are not identical; the bond formed by the 2s orbital is different from those formed by the 2p orbitals. Thus, the reason is **false**.

6. **Conclusion:**
- Since the assertion is true and the reason is false, the correct option is that the assertion is true but the reason is false.

**Final Answer:**
- The correct option is: Assertion is true, Reason is false.

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