In a study of neurotransmitter release, a lab models the phosphate group in ATP as a tetrahedral PO unit with resonance among P–O bonds. Considering the electron-domain geometry around phosphorus in PO, which molecular geometry is expected?
- Trigonal planar
- Tetrahedral (correct answer)
- Square planar
- Seesaw
Explanation: This question assesses molecular geometry in tetrahedral ions like phosphate. VSEPR theory predicts tetrahedral geometry for four electron domains with no lone pairs. In PO₄³⁻, phosphorus has four bonds to oxygen, with resonance making them equivalent, resulting in four domains. Tetrahedral geometry is consistent because it minimizes repulsion among the four bonding domains, matching observed symmetry. Choice C fails by suggesting square planar, which requires dsp² hybridization and is uncommon for phosphorus. Always count all bonding domains, considering resonance for equivalence. Verify by comparing to similar species like sulfate, which also exhibit tetrahedral geometry.