Which of the following pairs contains elements that are chemically dissimilar ?

Options

A. Na and K
B. Ba and Sr
C. Zr and Hf
D. Ca and Zn

Explanation

To determine which of the given pairs contains elements that are chemically dissimilar, we need to analyze the groups of the elements in each pair. Elements that belong to the same group in the periodic table typically exhibit similar chemical properties, while those from different groups tend to be chemically dissimilar.

### Step-by-Step Solution:

1. **Identify the pairs of elements**: We need to look at the pairs provided in the question. Let's assume the pairs are:
- Pair 1: Sodium (Na) and Potassium (K)
- Pair 2: Barium (Ba) and Strontium (Sr)
- Pair 3: Zirconium (Zr) and Hafnium (Hf)
- Pair 4: Calcium (Ca) and Zinc (Zn)

2. **Determine the group of each element**:
- **Sodium (Na)** and **Potassium (K)**: Both belong to Group 1 (Alkali metals).
- **Barium (Ba)** and **Strontium (Sr)**: Both belong to Group 2 (Alkaline earth metals).
- **Zirconium (Zr)** and **Hafnium (Hf)**: Both belong to Group 4 (Transition metals).
- **Calcium (Ca)**: Belongs to Group 2 (Alkaline earth metals).
- **Zinc (Zn)**: Belongs to Group 12 (Transition metals).

3. **Analyze chemical similarities**:
- Since Sodium and Potassium are in the same group, they will have similar chemical properties.
- Barium and Strontium are also in the same group, so they will have similar chemical properties.
- Zirconium and Hafnium are in the same group as well, so they will also have similar chemical properties.
- Calcium (Group 2) and Zinc (Group 12) belong to different groups, which means they will have different chemical properties.

4. **Conclusion**: The pair that contains chemically dissimilar elements is **Calcium (Ca) and Zinc (Zn)**, as they belong to different groups in the periodic table.

### Final Answer:
The pair that contains elements that are chemically dissimilar is **Calcium (Ca) and Zinc (Zn)**.

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