Which of the following statement(s) regarding periodic properties is/are incorrect?

Options

A. Alkali metals have highest I.E. in respective period.
B. Noble gas have highest I.E. in respective period
C. First electron affinity of nitrogen is less than oxygen
D. F atom has smallest radius in periodic table

Answer

To determine which statements regarding periodic properties are incorrect, we will analyze each statement provided in the question step by step.

### Step 1: Analyze the first statement
**Statement:** Alkali metals have the highest ionization enthalpy in their respective period.

**Analysis:**
- Alkali metals, such as sodium (Na), have a single electron in their outermost shell (3s¹ for sodium).
- Ionization enthalpy is the energy required to remove an electron from an atom.
- Since alkali metals have a relatively low ionization enthalpy due to their single outer electron, this statement is incorrect. Alkali metals do not have the highest ionization enthalpy; rather, they have one of the lowest in their respective periods.

### Step 2: Analyze the second statement
**Statement:** Noble gases have the highest ionization enthalpy in their respective period.

**Analysis:**
- Noble gases, such as neon (Ne), have a complete outer shell (1s² 2s² 2p⁶ for neon).
- Due to their stable electronic configuration, removing an electron from noble gases requires a significant amount of energy, making this statement correct.

### Step 3: Analyze the third statement
**Statement:** The first electron affinity of nitrogen is less than that of oxygen.

**Analysis:**
- Electron affinity refers to the energy change when an electron is added to a neutral atom.
- Nitrogen has the electronic configuration of 1s² 2s² 2p³ (half-filled), which is relatively stable. Adding an electron would disrupt this half-filled configuration.
- Oxygen has the configuration of 1s² 2s² 2p⁴, which can accommodate an additional electron more easily.
- Therefore, nitrogen's electron affinity is indeed less than that of oxygen, making this statement correct.

### Step 4: Analyze the fourth statement
**Statement:** Fluorine atom has the smallest radius in the periodic table.

**Analysis:**
- While fluorine (F) has a small atomic radius, it is not the smallest in the entire periodic table.
- Hydrogen (H) has a smaller atomic radius than fluorine. Therefore, this statement is incorrect.

### Conclusion
The incorrect statements are:
1. Alkali metals have the highest ionization enthalpy in their respective period.
4. Fluorine atom has the smallest radius in the periodic table.

### Final Answer
The incorrect statements regarding periodic properties are the first and fourth statements.

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