The pair in which ions are isoelectronic with `Al^(3+)` is :

Options

A. `Br^(-) and Be^(2-)`
B. `Cl^(-) and Li^(+)`
C. `S^(2-) and K^(+)`
D. `O^(2-) and Mg^(2+)`

Explanation

To determine which ions are isoelectronic with \( \text{Al}^{3+} \), we need to first understand what isoelectronic means. Isoelectronic species are those that have the same number of electrons.

### Step-by-Step Solution:

1. **Determine the number of electrons in \( \text{Al}^{3+} \)**:
- The atomic number of aluminum (Al) is 13.
- In its neutral state, Al has 13 electrons.
- When it loses 3 electrons to form \( \text{Al}^{3+} \), it has:
\[ 13 - 3 = 10 \text{ electrons} \]

2. **Identify ions that have 10 electrons**:
- We need to find ions that also have 10 electrons to be isoelectronic with \( \text{Al}^{3+} \).
- Common ions to consider:
- \( \text{O}^{2-} \): Oxygen has an atomic number of 8. In its anionic form \( \text{O}^{2-} \), it gains 2 electrons:
\[ 8 + 2 = 10 \text{ electrons} \]
- \( \text{N}^{3-} \): Nitrogen has an atomic number of 7. In its anionic form \( \text{N}^{3-} \), it gains 3 electrons:
\[ 7 + 3 = 10 \text{ electrons} \]
- \( \text{F}^{-} \): Fluorine has an atomic number of 9. In its anionic form \( \text{F}^{-} \), it gains 1 electron:
\[ 9 + 1 = 10 \text{ electrons} \]
- \( \text{Ne} \): Neon is a noble gas with an atomic number of 10 and has 10 electrons in its neutral state.

3. **List the ions that are isoelectronic with \( \text{Al}^{3+} \)**:
- From our calculations, the ions that have 10 electrons are:
- \( \text{O}^{2-} \)
- \( \text{N}^{3-} \)
- \( \text{Ne} \)

4. **Select the correct pair**:
- The question asks for a pair of ions that are isoelectronic with \( \text{Al}^{3+} \).
- The correct pair from the options provided is \( \text{O}^{2-} \) and \( \text{N}^{3-} \).

### Final Answer:
The pair in which ions are isoelectronic with \( \text{Al}^{3+} \) is \( \text{O}^{2-} \) and \( \text{N}^{3-} \).

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