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

Zirconium and Hafnium show similar physical and chemical properties despite belonging to different transition series due to the phenomenon known as the Lanthanide Contraction.

Here are the steps to understand this:

1. The Lanthanide Contraction refers to the fact that the 5f orbitals, which are filled in the lanthanide series, do not shield the increasing nuclear charge effectively. This results in a decrease in atomic radii and ionic radii across the period.

2. Zirconium (Zr) and Hafnium (Hf) are in the same group of the periodic table. Zr is in the 5th period and Hf is in the 6th period.

3. Due to the Lanthanide Contraction, the atomic radii of the elements in the 6th period (like Hf) are very similar to the atomic radii of the elements in the 5th period (like Zr).

4. Because Zr and Hf have similar atomic radii, their chemical behavior is also similar. This is because chemical behavior is often determined by the size of the atom, which affects how it bonds with other atoms.

5. Therefore, despite Zirconium belonging to the 4d transition series and Hafnium to the 5d transition series, they show similar physical and chemical properties due to the Lanthanide Contraction.