Explain the difference between the and MOs for homonuclear diatomic molecules. How are bonding and antibonding orbitals different? Why are there two MOs and one MO? Why are the MOs degenerate? 3.
The Pauli exclusion principle No two electrons in an atom can have the same quantum numbers n, l, m , and m l s – this means that an orbital can never have more than two electrons in it The Aufbau or filling principle In multielectron atoms, the electrons fill up the available energy levels (orbitals) starting with the lowest available level Orbital energies The orbitals in a multielectron atom do not have the same size or energy as the corresponding orbitals in a hydrogen atom – this is because the electrons in them experience an effective nuclear charge (Z eff) that is different from 1 (one) Effective nuclear charge Each electron is attracted to the nucleus and repelled by
