Which of the following orders are correct for property indicated in brackets ? .

Options

A. `NH_(3)gtNF_(3)gtBF_(3)` (dipole moment)
B. `CI gt S gt O gt N` (electron affinity)
C. `Si gt Mg gt A1 gt Na` (first ionisation enthalpy)
D. `HCIO_(4) gt HBrO_(4) gt HIO_(4)(pK_(a) "values")`

Explanation

To solve the question regarding the correct order of properties indicated in brackets, we will analyze each option step by step.

### Step 1: Analyze Dipole Moments of NH3, NF3, and BF3
1. **NH3 (Ammonia)**:
- Structure: Nitrogen has a lone pair and three hydrogen atoms.
- The dipole moment is directed towards the nitrogen due to its higher electronegativity compared to hydrogen. The lone pair also contributes to the dipole moment.
- Resultant dipole moment is significant.

2. **NF3 (Nitrogen Trifluoride)**:
- Structure: Nitrogen is bonded to three fluorine atoms.
- The dipole moments from the N-F bonds point towards the fluorine atoms, but the lone pair on nitrogen causes some cancellation.
- Resultant dipole moment is less than that of NH3 but still non-zero.

3. **BF3 (Boron Trifluoride)**:
- Structure: Boron is bonded to three fluorine atoms.
- The dipole moments from the N-F bonds cancel each other out due to symmetry.
- Resultant dipole moment is zero.

**Conclusion for Step 1**: The order of dipole moments is:
\[ \text{NH3} > \text{NF3} > \text{BF3} \]

### Step 2: Analyze Electron Affinity of Cl, S, O, N
1. **Chlorine (Cl)**: Highest electron affinity due to its position in the periodic table.
2. **Sulfur (S)**: Has a higher electron affinity than oxygen due to the ability to accommodate an extra electron in its d-orbitals.
3. **Oxygen (O)**: Lower electron affinity than sulfur but higher than nitrogen.
4. **Nitrogen (N)**: Lowest electron affinity in this group.

**Conclusion for Step 2**: The order of electron affinity is:
\[ \text{Cl} > \text{S} > \text{O} > \text{N} \]

### Step 3: Analyze First Ionization Energy of Si, Mg, Al, Na
1. **Silicon (Si)**: Has a higher ionization energy due to its position in the periodic table.
2. **Aluminum (Al)**: Lower ionization energy than silicon but higher than magnesium and sodium.
3. **Magnesium (Mg)**: Has a stable electron configuration, thus requires more energy to remove an electron.
4. **Sodium (Na)**: Lowest ionization energy among these elements.

**Conclusion for Step 3**: The order of ionization energy is:
\[ \text{Si} > \text{Mg} > \text{Al} > \text{Na} \]

### Step 4: Analyze pKa Values of HClO4, HBrO4, HIO4
1. **HClO4 (Perchloric Acid)**: Highest acidity due to chlorine's high electronegativity.
2. **HBrO4 (Perbromic Acid)**: Lower acidity than HClO4 but higher than HIO4.
3. **HIO4 (Periodic Acid)**: Lowest acidity due to iodine's lower electronegativity.

**Conclusion for Step 4**: The order of acidity (and thus the reverse order of pKa values) is:
\[ \text{HClO4} < \text{HBrO4} < \text{HIO4} \]
Thus, the order of pKa values is:
\[ \text{HIO4} > \text{HBrO4} > \text{HClO4} \]

### Final Summary of Orders:
1. Dipole Moment: \( \text{NH3} > \text{NF3} > \text{BF3} \)
2. Electron Affinity: \( \text{Cl} > \text{S} > \text{O} > \text{N} \)
3. Ionization Energy: \( \text{Si} > \text{Mg} > \text{Al} > \text{Na} \)
4. pKa Values: \( \text{HIO4} > \text{HBrO4} > \text{HClO4} \)