Standard bond angles assume ideal geometry, but real molecules deviate. Key exceptions: (1) Bond angle in H2O is 104.5, not 109.5, because 2 lone pairs compress bonds. (2) In PH3 (93.3) and AsH3 (91.8), bond angles approach 90 degrees because larger central atoms have less tendency to hybridise (bonds use nearly pure p-orbitals). (3) In ClF3 (T-shaped), the two axial F atoms are pushed slightly toward each other by lone pairs, giving F-Cl-F axial angle of ~87.5 (not 90). (4) Bond angle in NO2 (134) is greater than 120 because the unpaired electron in NO2 repels less than a lone pair would. In NO2- (115), the lone pair compresses the angle below 120. (5) Bond angle in OF2 (103) < H2O (104.5) because F is more electronegative, pulling bonding electrons closer to itself and reducing bp-bp repulsion.