CHM 401


Covalent Bonding

Bonding between atoms occurs because electron pairs are shared between atoms.

Why does this cause a nuclear-nuclear attraction?

Accumulated electron density causes a net nuclear-nuclear attraction (increased electron-nuclear attraction is greater than the increased electron-electron repulsion)


Valence Bond Theory: at an elementary level, electrons occupy a volume of space and orbitals are constructed to match the electron occupation.

Molecular Orbital Theory: orbitals are constructed and then filled with electrons according to the Aufbau and Pauli Principles.


Lewis Dot Structures: the usual method of denoting VBT bonding

Classical description/rationalization: atoms in molecules strive to attain a rare gas electron configuration

This is probably a bad generalization for most of the Periodic Table

two electrons on each atom

eight electrons on each atom

Better: atoms share electrons in molecules to attain the minimum formal charges

Formal charge: found by splitting the electrons in each equally between the bonded atoms.

Oxidation number: found by assigning all the electrons in a bond to the more electronegative atom.

Reality : somewhere in between