The increasing order of the first ionization enthalpies of the elements B,P,S and F (lowest first) is:

Options

A. `F lt S lt P lt B`
B. `P lt S lt B lt F`
C. `B lt P lt S lt F`
D. `B lt S lt P lt F`

Answer

To determine the increasing order of the first ionization enthalpies of the elements Boron (B), Phosphorus (P), Sulfur (S), and Fluorine (F), we need to analyze their positions in the periodic table and the factors affecting ionization energy.

### Step-by-Step Solution:

1. **Understanding Ionization Enthalpy**:
- Ionization enthalpy is defined as the amount of energy required to remove an electron from an isolated gaseous atom in its ground state. The first ionization enthalpy refers to the energy needed to remove the first electron.

2. **Periodic Trends**:
- Ionization energy generally increases across a period (from left to right) due to the increase in nuclear charge and decrease in atomic size.
- Ionization energy decreases down a group (from top to bottom) because the outermost electrons are farther from the nucleus and are shielded by inner electrons.

3. **Position of Elements**:
- Boron (B) is in Group 13 (p-block) and Period 2.
- Phosphorus (P) is in Group 15 (p-block) and Period 3.
- Sulfur (S) is in Group 16 (p-block) and Period 3.
- Fluorine (F) is in Group 17 (p-block) and Period 2.

4. **Comparing Ionization Energies**:
- **Fluorine (F)**: Being in Group 17 and Period 2, it has a high ionization energy due to its small atomic size and high effective nuclear charge.
- **Boron (B)**: Being in Group 13 and Period 2, it has the lowest ionization energy among these elements because it has a larger atomic size compared to F.
- **Phosphorus (P)**: In Period 3, it has a half-filled p subshell (3p3), which is relatively stable, leading to a higher ionization energy than sulfur.
- **Sulfur (S)**: Also in Period 3, but with a partially filled p subshell (3p4), it has a lower ionization energy than phosphorus due to increased electron-electron repulsion in the same subshell.

5. **Conclusion**:
- Based on the above analysis, the increasing order of first ionization enthalpies is:
\[ \text{B} < \text{P} < \text{S} < \text{F} \]

### Final Answer:
The increasing order of the first ionization enthalpies of the elements B, P, S, and F is:
\[ \text{B} < \text{P} < \text{S} < \text{F} \]