An atom of mass number `15` and atomic number `7` captures an `alpha-`particle and then emits a proton. The mass number and atomic number of the resulting product will respectively be.

Options

A. 14 and 2
B. 15 and 3
C. 16 and 4
D. 18 and 8

Explanation

To solve the problem, we will follow these steps:

1. **Identify the initial atom's properties**: The atom has a mass number (A) of 15 and an atomic number (Z) of 7. This means it has 15 nucleons (protons + neutrons) and 7 protons.

2. **Understand the alpha particle**: An alpha particle consists of 2 protons and 2 neutrons. When the atom captures an alpha particle, we need to add these nucleons to the original atom.

3. **Calculate the new atomic number and mass number after capturing the alpha particle**:
- New mass number after capturing the alpha particle:
\[ A' = 15 + 4 = 19 \]
- New atomic number after capturing the alpha particle:
\[ Z' = 7 + 2 = 9 \]

4. **Account for the emission of a proton**: When the atom emits a proton, we need to subtract 1 from both the mass number and the atomic number.
- Mass number after emitting a proton:
\[ A'' = 19 - 1 = 18 \]
- Atomic number after emitting a proton:
\[ Z'' = 9 - 1 = 8 \]

5. **Final result**: The resulting product will have a mass number of 18 and an atomic number of 8.

Thus, the mass number and atomic number of the resulting product will respectively be **18 and 8**.