Molecules are groups of atoms that behave as a single unit. Some elements exist as molecules: hydrogen, oxygen, sulfur, and so forth. There are rules that can express a unique name for any given molecule, and a unique formula for any given name. 9.1: Energy and Covalent Bond Formation 9.2: Lewis Electron-Dot Structures 9.3: Single Covalent Bonds 9.4: Multiple Covalent Bonds 9.5: Coordinate Covalent Bond Each of the covalent bonds that we have looked at so far has involved each of the atoms that are bonding contributing one of the electrons to the shared pair. There is an alternate type of covalent bond in which one of the atoms provided both of the electrons in a shared pair. 9.6: Covalent Bonding in Polyatomic Ions Lewis structures for polyatomic ions follow the same rules as those for other covalent compounds. 9.7: Resonance Resonance is the use of two or more Lewis structures to represent the covalent bonding in a molecule. One of the valid structures is referred to as a resonance structure. It is now understood that the true structure of a molecule which displays resonance is that of an average or a hybrid of all the resonance structures. 9.8: Exceptions to the Octet Rule Every spring, millions of Americans file their income tax forms. The different rules determine how much tax a person pays. There are also exceptions to the rules. You pay less tax if you are married and/or have children. There are certain limits on how much money you can make before paying taxes. The rule is that you pay taxes, but there are also exceptions based on your personal situation. The bonding rules for molecules are generally applicable, but there are some exceptions allowed. 9.9: Bond Energy 9.10: VSEPR Theory 9.11: Molecular Shapes- No Lone Pairs on Central Atoms 9.12: Molecular Shapes - Lone Pair(s) on Central Atom 9.13: Periodic Trends- Electronegativity 9.14: Bond Polarity 9.15: Polar Molecules 9.16: Van der Waals Forces 9.17: Hydrogen Bonding Template:HideTOC