1.A Sigma and Pi Bonds

Covalent bonds are created when 2 atoms share a pair of electrons, as already discussed in general chemistry. Usually, each nuclei donates 1 electron, but a coordinate covalent bond is when 1 nucleus donates BOTH electrons.

The sigma-bond is the 1st covalent bond formed, where the electrons are localized (i.e. always spend the most time right) between the nuclei.

The pi-bond is where the 2 nuclei form additional covalent bonds (apart from the 1st) with another pair of electrons, thereby forming a double/triple bond.

1.A.1 Hybrid orbitals (sp3, sp2, sp, and their respective geometries)

1.A.2 Valence shell electron-pair repulsion (VSEPR) theory, predictions of shapes of molecules (e.g., NH3, H2O, CO2)

More info: http://www.chem.ox.ac.uk/vrchemistry/vsepr/intro/vsepr_main.html

1.A.3 Structural formulas

1.A.4 Delocalized electrons and resonance in ions and molecules