VSEPR theory and the shapes it predicts, with lone pairs that squeeze the angles; valence bond theory, sigma and pi bonds; and hybridisation from sp to sp3d2.
3 lessons, about 1 h 30 min3 simulations10 problems4 practice questionsPython in every lesson
Created by StemPy LabVSEPR theory predicts the shape of a molecule from the electron pairs around its central atom. The pairs repel and spread as far apart as they can: two in a line, three in a triangle, four in a tetrahedron, five in a trigonal bipyramid and six in an octahedron. Lone pairs repel more than bonding pairs, so they squeeze the bond angles.
Valence bond theory explains a covalent bond as the overlap of two half-filled atomic orbitals. As two hydrogen atoms approach, their energy falls to a minimum at the bond length. Head-on overlap along the line of the nuclei gives a sigma bond. Sideways overlap of p orbitals gives a weaker pi bond.
Hybridisation is the mixing of atomic orbitals of nearly equal energy into the same number of equivalent hybrid orbitals. sp hybrids point 180° apart, sp2 hybrids 120° apart and sp3 hybrids 109.5° apart. With d orbitals, sp3d gives a trigonal bipyramid and sp3d2 an octahedron.
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