Which of the following statement is incorrect ?

Options

A. Electron affinity of nitrogen and noble gases is zero
B. Cesium is the most electropositive element , while fluorine is the most electronegative element
C. Chlorine has the highest electron affinity among all the elements of periodic table
D. In any period , the atomic radius the noble gas is lowest.

Answer

To solve the question, we need to analyze each of the four statements provided and determine which one is incorrect.

### Step-by-Step Solution:

1. **Statement 1**: "The electro affinity of nitrogen and noble gases is 0."
- **Analysis**:
- Noble gases have a complete valence shell, so they do not attract additional electrons, resulting in an electron affinity of 0.
- Nitrogen exists as a diatomic molecule (N2) with a strong triple bond. The energy required to break this bond is high, and due to inter-electronic repulsion, nitrogen also has an electron affinity of 0.
- **Conclusion**: This statement is **true**.

2. **Statement 2**: "Cesium is the most electropositive element while Fluorine is the most electronegative element."
- **Analysis**:
- Cesium is indeed the most electropositive element because it is the largest alkali metal, making it easy to lose its outermost electron.
- Fluorine is the most electronegative element as it has a high tendency to attract electrons to complete its valence shell.
- **Conclusion**: This statement is **true**.

3. **Statement 3**: "Chlorine has the highest electron affinity among all the elements of the periodic table."
- **Analysis**:
- While fluorine is the most electronegative element, chlorine has a higher electron affinity than fluorine due to its larger size and the presence of vacant d-orbitals, which allows it to accommodate an additional electron more effectively.
- **Conclusion**: This statement is **true**.

4. **Statement 4**: "In any period, the atomic radius of the noble gas is lowest."
- **Analysis**:
- As we move across a period, atomic radius generally decreases due to increasing nuclear charge. However, noble gases do not follow this trend strictly. For example, helium has a larger radius than hydrogen, and neon has a larger radius than fluorine. This is due to the stability of fully filled orbitals in noble gases, which leads to a larger atomic radius compared to other elements in the same period.
- **Conclusion**: This statement is **false**.

### Final Answer:
The incorrect statement is **Statement 4**.