In the structure of `SF_4`, the lone pair of electrons on S is in.

Options

A. A equatorial position and there are two lone pair - bond pair repulsions at `90^@`
B. equatorial position and there are three lone pair - bond pair repulsions at `90^@`
C. axial position and there are three lone pair - bond pair repulsion at `90^@`.
D. axial position and there are two lone pair - bond pair repulsion at `90^@`.

Explanation

To determine the position of the lone pair of electrons in the structure of SF4 (sulfur tetrafluoride), we can follow these steps:

### Step-by-Step Solution:

1. **Determine the Valence Electrons**:
- Sulfur (S) has 6 valence electrons.
- Each fluorine (F) has 7 valence electrons, and there are 4 fluorine atoms.
- Total valence electrons = 6 (from S) + 4 × 7 (from F) = 6 + 28 = 34 valence electrons.

2. **Draw the Lewis Structure**:
- Place sulfur in the center and surround it with four fluorine atoms.
- Connect each fluorine to sulfur with a single bond (4 bonds use 8 electrons).
- Remaining electrons = 34 - 8 = 26 electrons.
- Distribute the remaining electrons to the fluorine atoms to satisfy their octets (each F needs 6 more electrons, using 24 electrons).
- This leaves us with 2 electrons, which will be placed on the sulfur atom as a lone pair.

3. **Determine the Steric Number**:
- The steric number is calculated as the number of bonded atoms plus the number of lone pairs.
- Here, there are 4 bonded fluorine atoms and 1 lone pair on sulfur.
- Steric number = 4 (bonded) + 1 (lone pair) = 5.

4. **Identify the Molecular Geometry**:
- With a steric number of 5, the electron geometry is trigonal bipyramidal.
- However, the presence of one lone pair alters the molecular shape.

5. **Determine the Position of the Lone Pair**:
- In a trigonal bipyramidal arrangement, there are two types of positions: axial and equatorial.
- The lone pair will occupy an equatorial position to minimize repulsion with the bonded pairs.
- This is because lone pairs occupy more space than bonding pairs, and placing the lone pair in the equatorial position minimizes the repulsion with the three fluorine atoms in the equatorial plane.

6. **Conclusion**:
- Therefore, the lone pair of electrons on sulfur in SF4 is located in the equatorial position.

### Final Answer:
The lone pair of electrons on S in SF4 is in the equatorial position.