Assertion : For hydrogen like species, energy of an electron in a particular orbit increases with increase in value of Z.
Reason : Electronegativity decreases across a period.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that for hydrogen-like species, the energy of an electron in a particular orbit increases with an increase in the value of Z (atomic number).
- For hydrogen-like atoms, the energy of an electron in the nth orbit is given by the formula:
\[ E_n = -\frac{Z^2 \cdot k}{n^2} \]
where \( k \) is a constant. This indicates that as Z increases, the energy (which is negative) becomes more negative, meaning the energy level is lower. However, since we are discussing the absolute value of energy, we can say that the energy increases (becomes less negative) with increasing Z.

2. **Understanding the Reason**:
- The reason states that electronegativity decreases across a period.
- This statement is incorrect. In fact, electronegativity generally increases across a period from left to right due to increasing nuclear charge and decreasing atomic size.

3. **Conclusion**:
- The assertion is true because the energy of an electron in a hydrogen-like species does increase with an increase in Z.
- The reason is false because electronegativity actually increases across a period, not decreases.

### Final Answer:
- The assertion is true, and the reason is false.