Predict the geometrical structure of each of the following molecules or ions: (a) NO2- (b) PH3 (c) PF5 (d) PCl4+.

Verified step by step guidance

1. Step 1: Determine the total number of valence electrons for each molecule or ion. For NO2-, count the valence electrons from nitrogen and oxygen, and add one extra electron for the negative charge. For PH3, count the valence electrons from phosphorus and hydrogen. For PF5, count the valence electrons from phosphorus and fluorine. For PCl4+, count the valence electrons from phosphorus and chlorine, and subtract one electron for the positive charge.
2. Step 2: Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the molecular geometry. Identify the central atom and count the number of bonding pairs and lone pairs around it. This will help determine the shape of the molecule.
3. Step 3: For NO2-, consider the resonance structures and the presence of a lone pair on the nitrogen atom. This will affect the molecular geometry, which is typically bent or angular.
4. Step 4: For PH3, note that phosphorus has one lone pair and three bonding pairs with hydrogen atoms. This results in a trigonal pyramidal shape due to the lone pair-bond pair repulsion.
5. Step 5: For PF5, phosphorus forms five bonds with fluorine atoms, resulting in a trigonal bipyramidal geometry. For PCl4+, phosphorus forms four bonds with chlorine atoms, leading to a tetrahedral geometry.