The atomic radius of cd is closest to :

Options

A. Ag
B. Hg
C. Cu
D. Ni

Answer

To determine which element has an atomic radius closest to that of cadmium (Cd), we need to analyze the periodic table and consider the effects of lanthanide contraction.

### Step-by-Step Solution:

1. **Identify the Position of Cadmium**:
Cadmium (Cd) is located in the 6th period of the periodic table and belongs to group 12.

2. **List the Given Elements**:
The elements provided in the question are Silver (Ag), Mercury (Hg), Copper (Cu), and Nickel (Ni).

3. **Determine the Period of Each Element**:
- Silver (Ag) is in the 5th period.
- Mercury (Hg) is in the 6th period.
- Copper (Cu) is in the 4th period.
- Nickel (Ni) is also in the 4th period.

4. **Consider the Effects of Lanthanide Contraction**:
The lanthanide contraction occurs due to the filling of the 4f subshell, which causes the atomic radius of elements in the 6th period to be smaller than expected. This contraction affects the size of elements like mercury (Hg), making it comparable to elements in the previous period.

5. **Compare the Atomic Radii**:
- Cadmium (Cd) is in the same group as mercury (Hg), and due to lanthanide contraction, the atomic radius of Hg is reduced, making it closer to that of Cd.
- Silver (Ag) is in the previous period (5th) and has a larger atomic radius than Cd.
- Copper (Cu) and Nickel (Ni) are both in the 4th period and have smaller atomic radii compared to Cd.

6. **Conclusion**:
Based on the analysis, the atomic radius of mercury (Hg) is closest to that of cadmium (Cd) due to the effects of lanthanide contraction.

### Final Answer:
The atomic radius of cadmium (Cd) is closest to that of **Mercury (Hg)**.

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