An `alpha`-particle captures (i) one electron, (ii) two electrons. In each case, what does it change to ?

Answer

To solve the problem, we need to analyze the changes that occur when an alpha particle captures electrons. An alpha particle is essentially a helium nucleus, which consists of 2 protons and 2 neutrons, giving it a mass number of 4 and an atomic number of 2.

### Step-by-Step Solution:

1. **Understanding the Alpha Particle**:
- An alpha particle is the nucleus of helium, represented as \( \text{He}^{2+} \).
- It has 2 protons and 2 neutrons, giving it a mass number of 4 and a positive charge of +2 due to the 2 protons.

2. **Case (i): Capturing One Electron**:
- When the alpha particle captures one electron, it gains a negative charge from the electron.
- The charge of the alpha particle changes from +2 to +1 (since +2 - 1 = +1).
- The atomic number remains the same (2 protons) and the mass number also remains the same (4 nucleons).
- Therefore, after capturing one electron, the alpha particle changes to a helium ion with a +1 charge, represented as \( \text{He}^{+} \).

3. **Case (ii): Capturing Two Electrons**:
- When the alpha particle captures two electrons, it gains two negative charges.
- The charge of the alpha particle changes from +2 to 0 (since +2 - 2 = 0).
- Again, the atomic number remains the same (2 protons) and the mass number remains the same (4 nucleons).
- Thus, after capturing two electrons, the alpha particle changes to a neutral helium atom, represented as \( \text{He} \).

### Final Results:
- After capturing **one electron**, the alpha particle becomes \( \text{He}^{+} \) (a helium ion with a +1 charge).
- After capturing **two electrons**, the alpha particle becomes \( \text{He} \) (a neutral helium atom).