The molecular geometry of the phosphate ion (PO43-) is tetrahedral. This geometry arises from the arrangement of the central phosphorus atom surrounded by four oxygen atoms.
In the phosphate ion, the phosphorus atom shares electrons with four oxygen atoms, forming sigma bonds. Since all of these bonds are equivalent, the electron pair geometry adopts a tetrahedral shape to minimize repulsion between the electron pairs. The bond angle in a perfect tetrahedron is approximately 109.5 degrees.
Additionally, the presence of a negative charge on the ion influences its geometry, but in this case, the tetrahedral structure remains stable and is not distorted due to lone pairs on the phosphorus atom. Thus, the molecular geometry of PO43- can be confidently described as tetrahedral.