`Na^(+ )` ion is isoelectronic with

Options

A. `Li^(+)`
B. `Mg^(2+)`
C. `Ca^(2+)`
D. `Ba^(2+)`

Explanation

To determine which ion is isoelectronic with the sodium ion (Na⁺), we first need to understand what is meant by "isoelectronic." Isoelectronic species are atoms or ions that have the same number of electrons.

### Step-by-Step Solution:

1. **Identify the Electron Configuration of Sodium (Na):**
- Sodium (Na) has an atomic number of 11, which means it has 11 electrons in its neutral state.
- The electron configuration of sodium is:
\[ 1s^2 2s^2 2p^6 3s^1 \]

2. **Determine the Electron Configuration of Sodium Ion (Na⁺):**
- When sodium loses one electron to form Na⁺, it loses the electron from the outermost shell (3s).
- Therefore, the electron configuration of Na⁺ is:
\[ 1s^2 2s^2 2p^6 \]
- This shows that Na⁺ has 10 electrons.

3. **Find Other Ions or Atoms with 10 Electrons:**
- We need to find other species that also have 10 electrons.
- The following ions and atoms have 10 electrons:
- Neon (Ne) - a noble gas with atomic number 10.
- Magnesium ion (Mg²⁺) - Magnesium has 12 electrons, and when it loses 2 electrons, it has 10 electrons.

4. **Conclusion:**
- Therefore, Na⁺ is isoelectronic with Neon (Ne) and Magnesium ion (Mg²⁺).

### Final Answer:
Na⁺ ion is isoelectronic with Ne (Neon) and Mg²⁺ (Magnesium ion).