Which of the following species is/are isoelectronic with Neon ?
(i) `N^(3-)` (ii) `Mg^(2+)`
(iii) `K^+` (iv) `Ca^(2+)`

Options

A. only (iv)
B. only (ii)
C. both (i) & (ii)
D. both (i) & (iii)

Explanation

To determine which species are isoelectronic with Neon, we need to identify the number of electrons in each species and compare them to Neon, which has 10 electrons.

### Step-by-Step Solution:

1. **Identify the number of electrons in Neon:**
- Neon (Ne) is a noble gas with an atomic number of 10, meaning it has 10 electrons.

2. **Calculate the number of electrons in each species:**
- **(i) N^(3-)**:
- Neutral nitrogen (N) has 7 electrons.
- Since it has a charge of 3- (gains 3 electrons), the total number of electrons is:
\[ 7 + 3 = 10 \text{ electrons} \]
- **(ii) Mg^(2+)**:
- Neutral magnesium (Mg) has 12 electrons.
- Since it has a charge of 2+ (loses 2 electrons), the total number of electrons is:
\[ 12 - 2 = 10 \text{ electrons} \]
- **(iii) K^+**:
- Neutral potassium (K) has 19 electrons.
- Since it has a charge of 1+ (loses 1 electron), the total number of electrons is:
\[ 19 - 1 = 18 \text{ electrons} \]
- **(iv) Ca^(2+)**:
- Neutral calcium (Ca) has 20 electrons.
- Since it has a charge of 2+ (loses 2 electrons), the total number of electrons is:
\[ 20 - 2 = 18 \text{ electrons} \]

3. **Compare the number of electrons:**
- N^(3-): 10 electrons (isoelectronic with Ne)
- Mg^(2+): 10 electrons (isoelectronic with Ne)
- K^+: 18 electrons (not isoelectronic with Ne)
- Ca^(2+): 18 electrons (not isoelectronic with Ne)

4. **Conclusion:**
- The species that are isoelectronic with Neon are N^(3-) and Mg^(2+).

### Final Answer:
The species that are isoelectronic with Neon are (i) N^(3-) and (ii) Mg^(2+).

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