The lanthanide contraction is responsible for the fact that

Options

A. Zn and Y have about the same radii
B. Zr and Nb have simtextlar oxidation state
C. Zr and Hf have almost the same radii
D. Zr and Zn have the same oxidation state

Answer

To solve the question regarding the lanthanide contraction and its effects, we can break down the reasoning step by step:

### Step 1: Understand Lanthanide Contraction
The lanthanide contraction refers to the phenomenon where the ionic radii of the lanthanide elements decrease more than expected as you move from one element to the next in the series. This occurs due to the poor shielding effect of the f-electrons, which results in a stronger effective nuclear charge felt by the outer electrons.

**Hint:** Remember that the lanthanide series consists of elements with f-orbitals, and the poor shielding leads to a greater pull on the outer electrons.

### Step 2: Identify the Consequences of Lanthanide Contraction
Due to the lanthanide contraction, elements in the same period or group can exhibit similar physical and chemical properties. For example, the ionic radii of Zr (Zirconium) and Hf (Hafnium) are very similar because of the contraction effect.

**Hint:** Think about how similar ionic radii can influence the chemical behavior of elements.

### Step 3: Analyze the Given Options
The question provides several pairs of elements and asks which pair is affected by the lanthanide contraction. We need to evaluate each pair:
- Zn and Y: These are not directly influenced by the lanthanide contraction.
- Zr and Nb: These elements have different properties and are not directly comparable due to lanthanide effects.
- Zr and Hf: These elements are in the same group and have similar ionic radii due to the lanthanide contraction.
- Zr and Zn: These elements are not in the same group and do not show similar oxidation states due to lanthanide effects.

**Hint:** Focus on the elements that are in the same group or period as they are more likely to be influenced by the lanthanide contraction.

### Step 4: Conclusion
From the analysis, we can conclude that the lanthanide contraction is responsible for the fact that Zr and Hf have almost the same radii. Therefore, the correct answer is option C.

**Final Answer:** Zr and Hf have almost the same radii due to lanthanide contraction.