WAEC Chemistry 2025 Theory — Question 17

Model answer

Covalent bond. In PH3 (phosphine), the central phosphorus atom shares three of its five valence electrons with three hydrogen atoms, each contributing one valence electron, forming three P-H covalent bonds. The remaining two valence electrons form a lone pair, giving PH3 a polar, trigonal pyramidal shape (H-P-H bond angle ~93.5 degrees, P-H bond length ~1.42 Angstrom).