From the following nuclei, choose the isotopes and isobars :
(i) 8p + 8n , (ii) 8p +9n , (iii)18p + 22n , (iv)20p + 20n

Answer

To solve the problem of identifying isotopes and isobars from the given nuclei, we will follow these steps:

### Step 1: Identify the Atomic Mass and Atomic Number of Each Nucleus

1. **Nucleus (i)**: 8 protons + 8 neutrons
- Atomic Mass (A) = 8 + 8 = 16
- Atomic Number (Z) = 8

2. **Nucleus (ii)**: 8 protons + 9 neutrons
- Atomic Mass (A) = 8 + 9 = 17
- Atomic Number (Z) = 8

3. **Nucleus (iii)**: 18 protons + 22 neutrons
- Atomic Mass (A) = 18 + 22 = 40
- Atomic Number (Z) = 18

4. **Nucleus (iv)**: 20 protons + 20 neutrons
- Atomic Mass (A) = 20 + 20 = 40
- Atomic Number (Z) = 20

### Step 2: Classify the Nuclei as Isotopes or Isobars

- **Isotopes**: Nuclei that have the same atomic number (Z) but different atomic masses (A).
- **Isobars**: Nuclei that have the same atomic mass (A) but different atomic numbers (Z).

### Step 3: Analyze the Nuclei

1. **Nucleus (i)** and **Nucleus (ii)**:
- Both have the same atomic number (Z = 8) but different atomic masses (A = 16 for (i) and A = 17 for (ii)).
- Therefore, **Nucleus (i)** and **Nucleus (ii)** are **isotopes**.

2. **Nucleus (iii)** and **Nucleus (iv)**:
- Both have the same atomic mass (A = 40) but different atomic numbers (Z = 18 for (iii) and Z = 20 for (iv)).
- Therefore, **Nucleus (iii)** and **Nucleus (iv)** are **isobars**.

### Final Classification

- **Isotopes**:
- Nucleus (i) - 8 protons + 8 neutrons (A = 16)
- Nucleus (ii) - 8 protons + 9 neutrons (A = 17)

- **Isobars**:
- Nucleus (iii) - 18 protons + 22 neutrons (A = 40)
- Nucleus (iv) - 20 protons + 20 neutrons (A = 40)

### Summary

- Isotopes: (i) 8p + 8n and (ii) 8p + 9n
- Isobars: (iii) 18p + 22n and (iv) 20p + 20n

---