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 determine which statement is incorrect, we will analyze each option step by step.

### Step 1: Analyze Option 1
**Statement:** Electron affinity of nitrogen and noble gas is zero.

**Explanation:**
- Electron affinity is the energy change when an electron is added to a neutral atom to form a negative ion.
- Noble gases have a completely filled valence shell, making them stable and unlikely to accept an electron. Therefore, their electron affinity is indeed zero.
- Nitrogen has a half-filled 2p orbital configuration, which is stable, and thus its electron affinity is also effectively zero.

**Conclusion:** This statement is correct.

### Step 2: Analyze Option 2
**Statement:** Cesium is the most electropositive element while fluorine is the most electronegative element.

**Explanation:**
- Electropositivity refers to the tendency of an atom to lose electrons and form positive ions. Cesium, being an alkali metal, has the highest electropositive character in its group.
- Fluorine is indeed the most electronegative element, meaning it has a strong tendency to attract electrons.

**Conclusion:** This statement is correct.

### Step 3: Analyze Option 3
**Statement:** Chlorine has the highest electron affinity among all the elements of the periodic table.

**Explanation:**
- Electron affinity generally increases across a period and decreases down a group.
- While halogens have high electron affinities, fluorine has a higher electron affinity than chlorine due to its smaller atomic size and higher effective nuclear charge. Chlorine's electron affinity is lower than that of fluorine.

**Conclusion:** This statement is incorrect.

### Step 4: Analyze Option 4
**Statement:** In any period, the atomic radius of the noble gas is lowest.

**Explanation:**
- Atomic radius generally decreases across a period due to increasing nuclear charge, which pulls electrons closer to the nucleus.
- However, after the halogens, the atomic radius does not continue to decrease for noble gases; instead, it can be larger due to the lack of covalent bonding and the presence of only Van der Waals forces.

**Conclusion:** This statement is incorrect.

### Final Conclusion
The incorrect statements are Option 3 and Option 4. However, since the question asks for one incorrect statement, we can conclude that **Option 3** is the most directly incorrect regarding electron affinity.