In which two metals in the following pairs the difference between the covalent radii is maximum?

Options

A. `K, Ca`
B. `Mn , Fe`
C. `Co, Ni`
D. `Cr, Mn`

Answer

To solve the question of which two metals have the maximum difference between their covalent radii from the given pairs, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Pairs of Metals**:
The question provides several pairs of metals. We need to analyze each pair to determine the difference in their covalent radii.

2. **Understand Covalent Radii**:
Covalent radius is a measure of the size of an atom that forms part of a covalent bond. Generally, as you move across a period in the periodic table from left to right, the covalent radius decreases due to an increase in effective nuclear charge.

3. **Analyze Each Pair**:
- **Pair 1: Potassium (K) and Calcium (Ca)**:
- Potassium is in Group 1 (alkali metals), and Calcium is in Group 2 (alkaline earth metals).
- As we move from K to Ca, we are moving from Group 1 to Group 2, which generally results in a larger difference in size.

- **Pair 2: Manganese (Mn) and Iron (Fe)**:
- Both are d-block elements in the 3d series. The difference in their covalent radii is less significant because they are close in the periodic table.

- **Pair 3: Cobalt (Co) and Nickel (Ni)**:
- Similar to Mn and Fe, Co and Ni are also d-block elements and will have a small difference in their covalent radii.

- **Pair 4: Chromium (Cr) and Manganese (Mn)**:
- Again, both are d-block elements, and the difference in their covalent radii will be minimal.

4. **Compare the Differences**:
- The difference in covalent radii between K and Ca is expected to be larger than the differences between the other pairs (Mn-Fe, Co-Ni, Cr-Mn) because K is an alkali metal and Ca is an alkaline earth metal, which are further apart in the periodic table.

5. **Conclusion**:
- After analyzing all pairs, the maximum difference in covalent radii is between Potassium (K) and Calcium (Ca).

### Final Answer:
The two metals in which the difference between the covalent radii is maximum are **Potassium (K) and Calcium (Ca)**.

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