Which of the following are isoelectronic species ?
`overset(o+)(CH_(3))(I), overset(ɵ)(NH_(2))(II), overset(o+)(NH_(4))(III)` and `NH_(3) (IV)`

Options

A. II, III and IV
B. I, II and III
C. I, II and IV
D. II and I

Explanation

To determine which of the given species are isoelectronic, we need to find out the total number of electrons in each species. Isoelectronic species have the same number of electrons. Let's analyze each species one by one.

### Step 1: Calculate the number of electrons in each species

1. **For CH₃⁺ (I)**:
- Carbon (C) has 6 electrons.
- Each Hydrogen (H) has 1 electron, and there are 3 Hydrogens: 3 × 1 = 3 electrons.
- Total electrons = 6 (from C) + 3 (from H) = 9 electrons.
- Since it has a +1 charge, we subtract 1 electron:
- Total = 9 - 1 = 8 electrons.

2. **For NH₂⁻ (II)**:
- Nitrogen (N) has 7 electrons.
- Each Hydrogen (H) has 1 electron, and there are 2 Hydrogens: 2 × 1 = 2 electrons.
- Total electrons = 7 (from N) + 2 (from H) = 9 electrons.
- Since it has a -1 charge, we add 1 electron:
- Total = 9 + 1 = 10 electrons.

3. **For NH₄⁺ (III)**:
- Nitrogen (N) has 7 electrons.
- Each Hydrogen (H) has 1 electron, and there are 4 Hydrogens: 4 × 1 = 4 electrons.
- Total electrons = 7 (from N) + 4 (from H) = 11 electrons.
- Since it has a +1 charge, we subtract 1 electron:
- Total = 11 - 1 = 10 electrons.

4. **For NH₃ (IV)**:
- Nitrogen (N) has 7 electrons.
- Each Hydrogen (H) has 1 electron, and there are 3 Hydrogens: 3 × 1 = 3 electrons.
- Total electrons = 7 (from N) + 3 (from H) = 10 electrons.

### Step 2: Compare the total number of electrons

- **CH₃⁺** has 8 electrons.
- **NH₂⁻** has 10 electrons.
- **NH₄⁺** has 10 electrons.
- **NH₃** has 10 electrons.

### Step 3: Identify isoelectronic species

From the calculations:
- **NH₂⁻**, **NH₄⁺**, and **NH₃** all have 10 electrons, making them isoelectronic.
- **CH₃⁺** has 8 electrons and is not isoelectronic with the others.

### Conclusion

The isoelectronic species among the given options are **NH₂⁻ (II)**, **NH₄⁺ (III)**, and **NH₃ (IV)**.

### Final Answer:
The correct option is **II, III, and IV**.

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