Successive emission of an `alpha` - particle and two `beta`- particles by an atom of an element results in the formation of its :

Options

A. Isodiapher
B. Isobar
C. Isotope
D. Isotone

Explanation

To solve the problem of determining the resulting element after the successive emission of an alpha particle and two beta particles, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Alpha Decay**:
- An alpha particle consists of 2 protons and 2 neutrons. When an atom emits an alpha particle, its atomic number decreases by 2 and its atomic mass decreases by 4.
- If we denote the original element as having an atomic number \( Z \) and atomic mass \( A \), after one alpha decay, the new atomic number will be \( Z - 2 \) and the new atomic mass will be \( A - 4 \).

2. **Understanding Beta Decay**:
- A beta particle is essentially an electron emitted from the nucleus when a neutron is converted into a proton. This process increases the atomic number by 1 while keeping the atomic mass the same.
- After the first beta decay, the atomic number will increase by 1, resulting in \( Z - 1 \) and the atomic mass remains \( A - 4 \).

3. **Second Beta Decay**:
- Performing another beta decay on the new element (with atomic number \( Z - 1 \)), the atomic number will again increase by 1, resulting in \( Z \) (the atomic number returns to its original value), and the atomic mass remains \( A - 4 \).

4. **Final Result**:
- After the alpha particle emission and two beta particle emissions, the final element will have the same atomic number \( Z \) as the original element but a reduced atomic mass \( A - 4 \).
- This means the resulting atom is an isotope of the original element.

### Conclusion:
The final result of the successive emissions of one alpha particle and two beta particles from an atom of an element results in the formation of an isotope of that element.

### Answer:
The answer is **C: Isotope of the original element**.