To solve the question regarding the increase in atomic number during nuclear reactions, we will analyze the four types of emissions mentioned: Alpha emission, Beta emission, Positron emission, and Electron capture.
### Step-by-Step Solution:
1. **Understanding Alpha Emission:**
- In alpha emission, a nucleus emits an alpha particle (which consists of 2 protons and 2 neutrons).
- The general reaction can be represented as:
\[
\text{X} \rightarrow \text{Y} + \alpha
\]
- Here, the atomic mass decreases by 4 and the atomic number decreases by 2.
- Thus, alpha emission **does not** result in an increase in atomic number.
2. **Understanding Beta Emission:**
- In beta emission, a neutron in the nucleus is converted into a proton, emitting a beta particle (an electron).
- The general reaction can be represented as:
\[
\text{X} \rightarrow \text{Y} + \beta^-
\]
- In this case, the atomic mass remains the same, but the atomic number increases by 1.
- Therefore, beta emission **does** result in an increase in atomic number.
3. **Understanding Positron Emission:**
- In positron emission, a proton in the nucleus is converted into a neutron, emitting a positron (the antimatter counterpart of an electron).
- The general reaction can be represented as:
\[
\text{X} \rightarrow \text{Y} + \beta^+
\]
- Here, the atomic mass remains the same, but the atomic number decreases by 1.
- Thus, positron emission **does not** result in an increase in atomic number.
4. **Understanding Electron Capture:**
- In electron capture, an electron is captured by the nucleus, which combines with a proton to form a neutron.
- The general reaction can be represented as:
\[
\text{X} + e^- \rightarrow \text{Y}
\]
- The atomic mass remains the same, but the atomic number decreases by 1.
- Therefore, electron capture **does not** result in an increase in atomic number.
### Conclusion:
From the analysis above, the only process that results in an increase in atomic number is **Beta emission**.
### Final Answer:
The increase in atomic number is observed during **Beta emission**.
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