A pentagonal bipyramidal geometry is characterized by a central atom bonded to seven other atoms. In this structure, five atoms lie in an equatorial plane, forming a regular pentagon, and two atoms are in axial positions, one above and one below the plane.

Step 1: Analyze the equatorial plane.
The five atoms in the equatorial plane form a regular pentagon around the central atom. The angle between any two adjacent bonds in a regular pentagon is calculated as $\frac{360^{\circ }}{5}=72^{\circ }$. So, the bond angles within the equatorial plane are $72^{\circ }$.

Step 2: Analyze the axial bonds.
The two axial bonds are perpendicular to the equatorial plane. Therefore, the angle between an axial bond and any equatorial bond is $90^{\circ }$.

Step 3: Analyze the angle between axial bonds.
The two axial bonds are directed opposite to each other, forming a straight line through the central atom. Thus, the angle between the two axial bonds is $180^{\circ }$.

Step 4: Combine the angles.
The approximate bond angles present in a pentagonal bipyramidal structure are $72^{\circ }$ (equatorial-equatorial), $90^{\circ }$ (axial-equatorial), and $180^{\circ }$ (axial-axial).

Option Analysis:

• A) 120°, 90°, 180°: $120^{\circ }$ is incorrect for the equatorial angle.
• B) 120°, 72°, 180°: $120^{\circ }$ is incorrect for the equatorial angle, and $72^{\circ }$ is correct for equatorial but $90^{\circ }$ is missing for axial-equatorial.
• C) 72°, 90°, 120°: $120^{\circ }$ is incorrect, and $180^{\circ }$ (axial-axial) is missing.
• D) 72°, 90°, 180°: This option correctly lists all the characteristic bond angles for a pentagonal bipyramidal geometry.

Correct Answer: (D)