Which of the following order is correct for the property mentioned in brackets?

Options

A. `S^(2-) gt Cl^(-) gt K^(+) gt Ca^(2+)` (Ionization energy)
B. `C lt N lt F lt O` (2nd ionisation energy)
C. `B gt Al gt Ga gt In gt Tl` (Electronegativity)
D. `Na^(+) gt Li^(+) gt Mg^(2+) gt Be^(2+) gt Al^(3+) ` (Ionic radius)

Explanation

To solve the question regarding the correct order of the given properties, we will analyze each property step by step.

### Step 1: Understand Ionization Energy
**Definition**: Ionization energy is the energy required to remove an electron from an isolated gaseous atom.

**Trend**: Ionization energy generally increases across a period (left to right) due to decreasing atomic size and increasing nuclear charge. Conversely, it decreases down a group because of increasing atomic size.

**Analysis**: In the question, if the order suggests that anions have greater ionization energy than cations, this is incorrect. Anions are larger due to additional electrons, leading to less effective nuclear charge felt by the outermost electron, thus requiring less energy to remove an electron.

### Step 2: Evaluate Second Ionization Energy
**Definition**: Second ionization energy is the energy required to remove a second electron after the first has been removed.

**Trend**: The second ionization energy generally increases across a period due to increased effective nuclear charge and decreased size.

**Analysis**: For elements like carbon, nitrogen, oxygen, and fluorine, after the removal of one electron, the remaining configuration plays a crucial role. Oxygen (O) becomes O⁺ with a half-filled p subshell, which is more stable, thus requiring more energy to remove the next electron compared to the others. Therefore, the order of second ionization energy is correct as stated in the question.

### Step 3: Analyze Electronegativity
**Definition**: Electronegativity is the tendency of an atom to attract shared electrons in a chemical bond.

**Trend**: Electronegativity generally increases across a period and decreases down a group due to increasing atomic size.

**Analysis**: The order given in the question suggests an unusual trend among boron, aluminum, gallium, indium, and thallium. However, due to the increasing size and shielding effect down the group, the expected trend is not followed. Thus, the order provided in the question is incorrect.

### Step 4: Assess Ionic Radius
**Definition**: Ionic radius is the measure of an atom's ion in a crystal lattice.

**Trend**: Cations are smaller than their parent atoms due to loss of electrons and reduced electron-electron repulsion. Anions are larger due to the addition of electrons.

**Analysis**: The order given in the question suggests that Al³⁺ is larger than Ba²⁺, which is incorrect. Al³⁺ is indeed smaller than Ba²⁺ due to the higher charge density of Al³⁺, which pulls the electrons closer to the nucleus. Therefore, this order is also incorrect.

### Conclusion
Based on the analysis:
- The correct order for the second ionization energy is confirmed to be correct.
- The orders for ionization energy, electronegativity, and ionic radius are incorrect.

**Final Answer**: The correct order is given by option 2 (the order of second ionization energy).

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