Which of the following `is//are` example `(s)` if diagonal pairs?

Options

A. `Li and Na`
B. `Li and Be`
C. `Li and Mg`
D. `Be and Al`

Answer

To determine which of the given pairs are examples of diagonal pairs in the periodic table, we can follow these steps:

### Step 1: Understand Diagonal Relationships
Diagonal pairs in the periodic table refer to elements that are situated diagonally to each other, typically in different groups but similar in some chemical properties. This phenomenon is often observed in the s-block and p-block elements.

### Step 2: Analyze the Given Options
We have four options to evaluate:
1. Lithium and Sodium
2. Lithium and Beryllium
3. Lithium and Magnesium
4. Beryllium and Aluminium

### Step 3: Locate the Elements on the Periodic Table
- **Lithium (Li)** is in Group 1, Period 2.
- **Sodium (Na)** is in Group 1, Period 3.
- **Beryllium (Be)** is in Group 2, Period 2.
- **Magnesium (Mg)** is in Group 2, Period 3.
- **Aluminium (Al)** is in Group 13, Period 3.

### Step 4: Evaluate Each Pair
1. **Lithium and Sodium**: Both are in the same group (Group 1), so they are not diagonal pairs.
2. **Lithium and Beryllium**: Both are in the same period (Period 2), so they are not diagonal pairs.
3. **Lithium and Magnesium**: Lithium is in Group 1 and Magnesium is in Group 2, but they are in different periods (Lithium in Period 2 and Magnesium in Period 3), making them diagonal pairs.
4. **Beryllium and Aluminium**: Beryllium is in Group 2 and Aluminium is in Group 13, and they are in different periods (Beryllium in Period 2 and Aluminium in Period 3), making them diagonal pairs.

### Step 5: Conclusion
The correct pairs that are examples of diagonal pairs are:
- **Lithium and Magnesium**
- **Beryllium and Aluminium**

Thus, the correct options are C (Lithium and Magnesium) and D (Beryllium and Aluminium).

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