A radio-active elements emits one `alpha` and `beta` particles then mass no. of daughter element is :

Options

A. Decreased by 4
B. Increased by 4
C. Decreased by 2
D. Increased by 2

Answer

To solve the problem, we need to determine the mass number of the daughter element after a radioactive element emits one alpha particle and one beta particle.

### Step-by-Step Solution:

1. **Understand the Emission of Particles**:
- An alpha particle (α) is a helium nucleus, which consists of 2 protons and 2 neutrons. Therefore, it has a mass number of 4.
- A beta particle (β) is an electron, which has a negligible mass compared to the mass of an alpha particle and does not affect the mass number significantly.

2. **Initial Mass Number**:
- Let the mass number of the parent radioactive element be denoted as \( A \).

3. **Effect of Alpha Particle Emission**:
- When an alpha particle is emitted, the mass number decreases by 4. Thus, after the emission of the alpha particle, the mass number becomes:
\[ A - 4 \]

4. **Effect of Beta Particle Emission**:
- The emission of a beta particle does not change the mass number, as the beta particle is an electron and has negligible mass. Therefore, the mass number remains:
\[ A - 4 \]

5. **Final Mass Number of Daughter Element**:
- After both emissions, the mass number of the daughter element is:
\[ A' = A - 4 \]

### Conclusion:
The mass number of the daughter element after the emission of one alpha and one beta particle is \( A - 4 \).