In first transition series which of the following has lowest enthalpy of atomisation?

Options

A. Sc
B. Cu
C. Ti
D. Zn

Answer

To determine which element in the first transition series has the lowest enthalpy of atomization, we need to analyze the electronic configurations and the stability of the elements in question. The elements provided are Scandium (Sc), Chromium (Cr), Titanium (Ti), and Zinc (Zn).

### Step-by-Step Solution:

1. **Identify the Elements and Their Electronic Configurations**:
- Scandium (Sc): [Ar] 3d¹ 4s²
- Titanium (Ti): [Ar] 3d² 4s²
- Chromium (Cr): [Ar] 3d⁵ 4s¹ (Note: Chromium has a half-filled d-subshell which provides extra stability)
- Zinc (Zn): [Ar] 3d¹⁰ 4s²

2. **Understand Enthalpy of Atomization**:
- The enthalpy of atomization is the energy required to separate one mole of a substance into its gaseous atoms. Generally, elements with fully filled or half-filled d-orbitals tend to have lower enthalpy of atomization due to their increased stability.

3. **Analyze Stability**:
- **Zinc (Zn)** has a completely filled d-subshell (3d¹⁰) and a filled s-subshell (4s²), making it very stable. This stability results in a lower enthalpy of atomization.
- **Scandium (Sc)** and **Titanium (Ti)** have partially filled d-orbitals, which means they are less stable compared to Zinc.
- **Chromium (Cr)** has a half-filled d-subshell, which is stable but not as stable as a fully filled d-subshell.

4. **Conclusion**:
- Among the given elements, Zinc (Zn) has the lowest enthalpy of atomization due to its fully filled d-orbital (3d¹⁰) and filled s-orbital (4s²), which makes it more stable compared to the other elements.

### Final Answer:
Zinc (Zn) has the lowest enthalpy of atomization in the first transition series.