CF₄: tetrahedral, 109°28′; NF₃: trigonal pyramidal, about 102°; HCN: linear, 180°; H₂S: bent (angular), about 92°.
- a. \(\mathrm{CF_4}\): C has 4 bond pairs and no lone pair (sp³). Shape: regular tetrahedral; F–C–F = 109°28′.
- b. \(\mathrm{NF_3}\): N has 3 bond pairs and 1 lone pair (sp³), like \(\mathrm{NH_3}\). Shape: trigonal pyramidal; the lone pair repulsion makes F–N–F less than 109°28′ (measured about 102°).
- c. HCN: H–C≡N. C has two σ bonds (to H and N) and no lone pair (sp). Shape: linear; H–C–N = 180°.
- d. \(\mathrm{H_2S}\): S has 2 bond pairs and 2 lone pairs, like water. Shape: bent (V-shaped); the angle is less than 109°28′, measured about 92° (smaller than in \(\mathrm{H_2O}\) because S is larger and less electronegative than O).
In general: 4 electron pairs around the central atom with 0, 1 or 2 lone pairs give tetrahedral, pyramidal or bent shapes; 2 electron domains with no lone pairs give a linear shape.
