8.1 Molecular Compounds

• Molecular compounds tend to have relatively low melting and boiling points.
• A molecular formula shows how many atoms of each element a molecule contains.

8.2 The Nature of Covalent Bonding

• Electron sharing occurs so that atoms attain the configurations of noble gases.
• An electron dot structure shows the shared electrons of a covalent bond by a pair of dots.
• Atoms form double or triple bonds by sharing two or three pairs of electrons.
• In a coordinate covalent bond, the shared electron pair comes from a single atom.
• A large bond dissociation energy corresponds to a strong covalent bond.
• In ozone, the bonding of oxygen atoms is a hybrid of the extremes represented by the resonance forms.
• The octet rule is not satisfied in molecules with an odd number of electrons, and in molecules where an atom has less, or more, than a complete octet of valence electrons.

8.3 Bonding Theories

• Just as an atomic orbital belongs to a particular atom, a molecular orbital belongs to a molecule as a whole.
• According to VSEPR theory, the repulsion between electron pairs causes molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible.
• Orbital hybridization provides information about both molecular bonding and molecular shape.

8.4 Polar Bonds and Molecules

• When different atoms bond, the more electronegative atom attracts electrons more strongly and acquires a slight negative charge.
• Polar molecules between oppositely charged metal plates tend to become oriented with respect to the positive and negative plates.
• Intermolecular attractions are weaker than either an ionic or covalent bond.
• Melting a network solid requires breaking covalent bonds throughout the solid.