(A): Electron affinity of fluorine is lower than that of chlorine
(R): Fluorine has small and compact size and stronger inter electron repulsion than chlorine.

Options

A. Both A & R are true, R is the correct explanation of A
B. Both A & R are true, R is not correct explanation of A
C. A is true, R is false
D. A is false, R is true

Answer

To analyze the assertion and reason provided in the question, we can break it down into a step-by-step solution.

### Step 1: Understand the Assertion
The assertion states that the electron affinity of fluorine is lower than that of chlorine. Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gas phase.

### Step 2: Understand the Reason
The reason given is that fluorine has a small and compact size, which leads to stronger inter-electron repulsion compared to chlorine. This suggests that the addition of an electron to fluorine is less favorable due to the repulsion between the electrons.

### Step 3: Analyze the Trend in Electron Affinity
In general, as we move down a group in the periodic table, the size of the atoms increases, and typically, the electron affinity decreases. This is because larger atoms can accommodate additional electrons more easily due to less electron-electron repulsion.

### Step 4: Compare Fluorine and Chlorine
Fluorine is indeed smaller than chlorine, which means that when an additional electron is added to fluorine, the electrons are closer together. This proximity leads to increased electron-electron repulsion, making the addition of the electron less favorable. In contrast, chlorine, being larger, has less inter-electron repulsion when an electron is added.

### Step 5: Conclusion
Based on the analysis, we conclude that the assertion is true: the electron affinity of fluorine is lower than that of chlorine. The reason provided is also true and correctly explains the assertion: the small size of fluorine leads to stronger inter-electron repulsion, which contributes to its lower electron affinity compared to chlorine.

### Final Answer
Both the assertion (A) and the reason (R) are true, and R is the correct explanation of A.

---