VSEPR theory explains molecular shapes based on electron pair repulsion. Gillespie and Nyholn developed this theory to explain valence shell electron pairs
SO3 contains one sulfur atom surrounded by three oxygen atoms. Each oxygen atom has two lone pairs of electrons. Total valence electrons are 24 (6S + 6O * 3)
Carbon and chlorine form a covalent compound by sharing electrons. Total valence electrons are 32 (4 from carbon, 4 from each chlorine). Carbon is placed as the central atom due to its low electronegativity
Hybridization combines atomic orbitals to form new orbitals with same energy and shape. Hybrid orbitals can be half-filled, completely filled, or vacant. Hybridization predicts the shape of covalent molecules
Chlorine exists as diatomic molecule Cl2 with two chlorine atoms. Each chlorine atom has three lone pairs. Molecule contains one single bond between chlorine atoms
NO2 contains one nitrogen atom bonded to two oxygen atoms. Total 17 valence electrons with one unpaired electron. Nitrogen is central atom surrounded by oxygen atoms