If a compound is `AB_4` is polar then its strcture is similar to

Options

A. Square planar
B. Tetrahedral
C. Trigonal bipyramidal
D. Rectangular planar

Answer

To determine the structure of a polar compound with the formula \( AB_4 \), we need to analyze the possible geometries and their effects on the dipole moment.

### Step-by-Step Solution:

1. **Understanding Polarity**:
- A molecule is polar if it has a net dipole moment that is non-zero. This means that the dipole moments of the individual bonds do not cancel each other out.

2. **Identifying Possible Geometries**:
- The possible geometries for \( AB_4 \) include:
- Tetrahedral
- Square planar
- Trigonal bipyramidal

3. **Analyzing Square Planar Geometry**:
- In a square planar geometry, the four \( B \) atoms are arranged in a square plane around the central atom \( A \).
- If \( B \) is more electronegative than \( A \), the dipole moments from each \( B \) will point towards \( B \).
- The dipole moments will cancel each other out due to symmetry, resulting in a net dipole moment of zero. Thus, a square planar structure is non-polar.

4. **Analyzing Tetrahedral Geometry**:
- In a tetrahedral geometry, the four \( B \) atoms are arranged around the central atom \( A \) in a three-dimensional shape.
- Similar to the square planar case, if \( B \) is more electronegative than \( A \), the dipole moments will also cancel out due to symmetry.
- Therefore, a tetrahedral structure is also non-polar.

5. **Analyzing Trigonal Bipyramidal Geometry**:
- In a trigonal bipyramidal geometry, there are five positions: three in a plane (equatorial) and two above and below the plane (axial).
- If one of the positions is occupied by a lone pair, the geometry becomes distorted.
- The dipole moments from the \( B \) atoms will not cancel out due to the presence of the lone pair, resulting in a net dipole moment that is non-zero. Hence, this structure can be polar.

6. **Conclusion**:
- The only geometry among the options that can result in a polar molecule is the trigonal bipyramidal geometry with a lone pair. Therefore, the structure of the polar compound \( AB_4 \) is similar to that of a trigonal bipyramidal geometry.

### Final Answer:
The structure of the polar compound \( AB_4 \) is similar to **trigonal bipyramidal**.