Select the correct statement(s) for positron emission by unstable nucleus.

Options

A. X-ray emission takes place
B. a neutron is formed
C. `(n)/(p)` of daughter nucleus increases
D. A neutron is consumed

Answer

### Step-by-Step Solution:

1. **Understanding Positron Emission**:
Positron emission is a type of radioactive decay where a proton in an unstable nucleus is transformed into a neutron, resulting in the emission of a positron (β+ particle). A positron is similar to an electron but carries a positive charge.

2. **Change in Atomic and Mass Numbers**:
- **Atomic Number (Z)**: The atomic number decreases by 1 because a proton is converted into a neutron.
- **Mass Number (A)**: The mass number remains the same because the total number of nucleons (protons + neutrons) does not change.

3. **Example of Positron Emission**:
If we consider a nucleus represented as \( _Z^A X \), during positron emission, it transforms into \( _{Z-1}^A Y + \beta^+ \), where \( Y \) is the new element formed after the decay.

4. **Characteristics of Positron Emission**:
- It typically occurs in proton-rich radionuclides.
- The process increases the neutron-to-proton (n/p) ratio in the nucleus because the number of protons decreases while the number of neutrons remains unchanged.

5. **Conclusion**:
The correct statements regarding positron emission include:
- A positron is emitted when a proton is converted into a neutron.
- The atomic number decreases by 1, while the mass number remains unchanged.
- This decay process is common in radionuclides that have an excess of protons.