Which of the following statement(s) is/are correct?

Options

A. van der waals' radius of iodine is more than its covalent radius
B. All isoelectronic ions of corresponding elements belong to the same period of the periodic table.
C. IE. Of N-atom is higher than that of O-atom, while `IE_(2)` of O-atom is higher than that of N-atom.
D. The electron affinity of fluorine is greater than that of chlorine.

Answer

To determine which of the statements provided are correct, we will analyze each statement one by one based on the principles of periodic properties.

### Step 1: Analyze the first statement
**Statement:** The Van der Waals radius of iodine is more than its covalent radius.

**Analysis:**
- The Van der Waals radius refers to the size of an atom when it is not bonded to another atom, while the covalent radius is the size of an atom when it is bonded to another atom.
- Van der Waals forces are weaker than covalent bonds, which means that atoms are more loosely packed in a Van der Waals interaction compared to a covalent bond.
- Therefore, the Van der Waals radius of iodine is indeed greater than its covalent radius.

**Conclusion:** This statement is **correct**.

### Step 2: Analyze the second statement
**Statement:** All isoelectronic ions corresponding elements belong to the same period of the periodic table.

**Analysis:**
- Isoelectronic species are atoms or ions that have the same number of electrons.
- For example, N³⁻ and Na⁺ both have 10 electrons but belong to different periods (N is in the second period and Na is in the third period).
- Therefore, it is not true that all isoelectronic ions belong to the same period.

**Conclusion:** This statement is **incorrect**.

### Step 3: Analyze the third statement
**Statement:** The ionization energy of nitrogen atom is higher than that of oxygen, while the second ionization energy of oxygen atom is higher than that of nitrogen atom.

**Analysis:**
- The first ionization energy (IE1) is the energy required to remove the outermost electron. Nitrogen has a half-filled p subshell (2p³), which gives it extra stability, making it harder to remove an electron compared to oxygen (2p⁴).
- Therefore, the first ionization energy of nitrogen is indeed higher than that of oxygen.
- For the second ionization energy (IE2), after the first electron is removed, nitrogen becomes 2p², and oxygen becomes 2p³. Removing another electron from oxygen (which has a stable half-filled configuration after the first removal) requires more energy than removing from nitrogen.
- Thus, the second ionization energy of oxygen is higher than that of nitrogen.

**Conclusion:** This statement is **correct**.

### Step 4: Analyze the fourth statement
**Statement:** The electron affinity of fluorine is greater than that of chlorine.

**Analysis:**
- Electron affinity refers to the energy change when an electron is added to a neutral atom.
- Although fluorine is more electronegative than chlorine, it has a smaller atomic radius and less space to accommodate an additional electron due to electron-electron repulsion in its small 2p orbital.
- Chlorine, being larger, can accommodate an extra electron more easily, resulting in a higher electron affinity.

**Conclusion:** This statement is **incorrect**.

### Final Summary of Statements
- Statement 1: Correct
- Statement 2: Incorrect
- Statement 3: Correct
- Statement 4: Incorrect

### Final Answer
The correct statements are: **1 and 3.**