Although Zirconium belongs to 4d transition series and Hafnium to 5d transition series even then they show similar physical and chemical properties because

Options

A. both belong to d-block.
B. both have same number of electrons.
C. both have similar atomic radii.
D. both belong to the same group of the periodic table

Explanation

To understand why Zirconium (Zr) and Hafnium (Hf) exhibit similar physical and chemical properties despite being in different transition series, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Identify the Elements and Their Series**:
- Zirconium (Zr) belongs to the 4d transition series.
- Hafnium (Hf) belongs to the 5d transition series.

2. **Group Position**:
- Both Zirconium and Hafnium are located in the same group (Group 4) of the periodic table. Elements in the same group often exhibit similar chemical properties due to their similar valence electron configurations.

3. **Electron Configuration**:
- Both elements have a similar number of electrons in their outermost shell, which contributes to their similar chemical behavior.

4. **Atomic Radii**:
- The atomic radii of Zirconium and Hafnium are similar. Zirconium has an atomic radius of approximately 160 pm, while Hafnium has an atomic radius of about 159 pm. This similarity in size is crucial for their comparable physical properties.

5. **Lanthanoid Contraction**:
- The key reason for the similarity in atomic size is the phenomenon known as lanthanoid contraction. This occurs due to the poor shielding effect of the f-electrons in the lanthanide series, which leads to a decrease in size as we move across the series.
- Hafnium is positioned below Lanthanum (La), and because of lanthanoid contraction, the atomic size of elements in the 5d series (like Hafnium) becomes comparable to that of the 4d series (like Zirconium).

6. **Conclusion**:
- Therefore, the similarity in physical and chemical properties between Zirconium and Hafnium can be attributed to their placement in the same group, similar electron configurations, and the effects of lanthanoid contraction leading to comparable atomic radii.

### Final Answer:
Zirconium and Hafnium show similar physical and chemical properties because they belong to the same group in the periodic table, have similar electron configurations, and their atomic sizes are comparable due to lanthanoid contraction.

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