Molecular Compounds
Definition
Substances that are composed of molecules are called molecular compounds
- Many non-metals form bonds with other non-metals to become stable
- The number of covalent bonds can be determined by looking at the element's charge as an anion
- The electrons are shared, not given
Bond counts
Figure
Types of Bonds
The type of covalent bond is determined by the electronegativity difference
Pure Covalent Bonds
Info
Polar/Dipole Covalent Bonds
Info
- Polar covalent molecules need molecule and bond polarity arrows
- Use 𝛿 (partial) to denote the positive and negative poles of the molecule
Example
Bond Energies
Definition
- The strength of a covalent bond depends on:
- Size of an atom
- Number of electrons shared
- Bond polarity
The amount of energy required to break (or released when) a covalent bond can be determined from bond energies (kJ/mol)
Examples
Properties
Info
Though bonds between atoms are strong, bonds between molecules are weak. As a result, many molecular compounds are liquids or gasses at room temperature.
Properties
- Low melting point
- Low boiling point
- (
) ( ) - Soft
- Odourous
- Insulators
Diatomic Molecules
Info
Diatomic molecules are also the result of covalent bonds
Examples
Mnemonic
Pronounced hof-brincl, "hoff-brinkle"
Drawing Lewis Line Diagrams
Steps
- Put the atom that makes the most bonds in the centre
- Draw other atoms around in WESN (?) format
- For outer atoms, make the max. possible bonds for each
Examples