Which pair show less similarity in their properties than the other three:

Options

A. Li–Mg
B. Be–Al
C. Na–Ca
D. B–Si

Answer

To determine which pair of elements shows less similarity in their properties than the other three pairs, we can analyze the given pairs based on their positions in the periodic table and their chemical properties.

### Step-by-Step Solution:

1. **Identify the pairs of elements:**
- The pairs mentioned are likely:
- Li and Mg (Lithium and Magnesium)
- Be and Al (Beryllium and Aluminum)
- Na and Ca (Sodium and Calcium)
- B and Si (Boron and Silicon)

2. **Analyze the first pair (Li and Mg):**
- Lithium (Li) is an alkali metal (Group 1) and Magnesium (Mg) is an alkaline earth metal (Group 2).
- Both belong to the same period (Period 2 for Li and Period 3 for Mg), but they have different group properties.
- However, they do share some similarities due to being adjacent in the periodic table.

3. **Analyze the second pair (Be and Al):**
- Beryllium (Be) is in Group 2 and Aluminum (Al) is in Group 13.
- These elements are diagonally related and exhibit similar properties, such as electronegativity and polarizing power.

4. **Analyze the third pair (Na and Ca):**
- Sodium (Na) is in Group 1 and Calcium (Ca) is in Group 2.
- Although they are both metals, their properties differ due to being in different groups, but they still share some similarities as they are both alkali and alkaline earth metals.

5. **Analyze the fourth pair (B and Si):**
- Boron (B) is in Group 13 and Silicon (Si) is in Group 14.
- They are also diagonally related and show similarities in their properties, particularly in their electronegativity and bonding characteristics.

6. **Comparison of similarities:**
- Li and Mg show some similarities due to their proximity in the periodic table.
- Be and Al show significant similarities due to their diagonal relationship.
- Na and Ca have some similarities but are less similar compared to the first two pairs.
- B and Si also show similarities due to their diagonal relationship.

7. **Conclusion:**
- The pair that shows the least similarity in their properties compared to the others is **Na and Ca**. While they are both metals, their properties differ more significantly than the other pairs.

### Final Answer:
The pair that shows less similarity in their properties than the other three is **Na and Ca**.