CHMA10H3 Lecture Notes - Lecture 27: Valence Bond Theory, Paramagnetism, Diamagnetism

• School: UTSC
• Department: Chemistry
• Course: CHMA10H3
• Professor: Marco Zimmer

Document Summary

Valence e- involved to explain both covalent and ionic bonds. Relatively easy and quick to do with just paper and pencil. Extension of lewis theory to explain shapes based on electrostatic repulsion of e- Can be used to correctly predict shapes of majority of molecules. Combine lewis and vsepr but bring in quantum mechanics and orbitals. Bonds explained as sharing of e- pairs but atomic orbitals must overlap in particular ways. Pi bond=present in double and triple bonds=indirect overlap. Vb theory predicts molecular oxygen should be diamagnetic: diamagnetic = all the e- are paired i. e. oxygen should not be affected by a magnetic field. Experiments show o2 is paramagnetic: paramagnetic = there are unpaired e- present in the molecule because it is attracted to a magnetic field. Molecular orbital theory (mot) is a more complete way of describing bonding. Magnetic properties of the molecules i. e. the paramagnetism of the o2 molecule.