The fact that can be explained based on lanthanide contraction is

Options

A. Zr and Y have about the same radius
B. Zr and Nb have similar oxidation state
C. Zr and Hf have about same radius
D. Zr and Zn have the same oxidation state.

Answer

To solve the question regarding the fact that can be explained based on lanthanide contraction, we will follow these steps:

### Step 1: Understand Lanthanide Contraction
Lanthanide contraction refers to the phenomenon where the atomic and ionic radii of the lanthanide series elements decrease despite the increase in atomic number. This occurs due to the poor shielding effect of the f-electrons, which leads to a stronger effective nuclear charge felt by the outer electrons.

**Hint:** Remember that lanthanide contraction affects elements in the periodic table that follow the lanthanides, particularly the transition metals.

### Step 2: Identify the Elements in Question
The question mentions zirconium (Zr) and hafnium (Hf). Zr is in the 5th period, while Hf is in the 6th period of the periodic table.

**Hint:** Look at the position of Zr and Hf in the periodic table to understand their relationship.

### Step 3: Compare the Atomic Radii
The atomic radius of zirconium (Zr) is approximately 159 pm, while that of hafnium (Hf) is about 156 pm. Despite the increase in atomic number from 40 (Zr) to 72 (Hf), the radii are quite similar.

**Hint:** Focus on the values of atomic radii and how they relate to the concept of contraction.

### Step 4: Analyze the Implications of Similar Radii
The similar radii of Zr and Hf imply that they exhibit similar chemical behavior and properties. This is because properties like lattice energy, solvation energy, and stability constants of complexes are influenced by atomic size.

**Hint:** Think about how atomic size affects chemical properties and interactions.

### Step 5: Conclusion
Based on the above analysis, the fact that can be explained based on lanthanide contraction is that zirconium (Zr) and hafnium (Hf) have about the same radius. This similarity arises due to the lanthanide contraction affecting the elements that follow the lanthanides in the periodic table.

**Hint:** Summarize the findings to clearly state the conclusion regarding Zr and Hf.

### Final Answer
The fact that can be explained based on lanthanide contraction is that zirconium (Zr) and hafnium (Hf) have about the same radius.