Why do Zr and Hf exhibits similar properties?
Why do transition metal show variable oxidation states.

Explanation

### Step-by-Step Text Solution:

**1. Similar Properties of Zr and Hf:**
- **Reason for Similar Properties:** Zirconium (Zr) and Hafnium (Hf) exhibit similar properties primarily due to the phenomenon known as **lanthanide contraction**.
- **Explanation of Lanthanide Contraction:**
- Lanthanide contraction refers to the gradual decrease in the size of the lanthanide series elements as the atomic number increases. This occurs because the f-electrons, which are being added to the f-orbitals, do not shield the nuclear charge effectively.
- As a result, the effective nuclear charge felt by the outer electrons increases, leading to a decrease in atomic size.
- **Impact on Zr and Hf:**
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