The covalent bond is a result of two positive nuclei being held together by their common attraction for the shared pair of electrons.

In a covalent bond, atoms share pairs of electrons.

Polar covalent bonds are formed when the attraction of the atoms for the pair of bonding electrons is different.

In polar covalent bonds the atoms have partial charges which give rise to a dipole.

There is specific notation used to indicate the partial negative and partial positive charges on atoms: δ+ — delta positive — is used to indicate a partial positive charge, and δ- — delta negative — is used to indicate a partial negative charge.

Ionic formulae is written giving the simplest ratio of each type of ion in the substance.

Ionic bonds are the electrostatic attraction between positive and negative ions.

Ionic compounds form lattice structures of oppositely charged ions.

Pure covalent bonding and ionic bonding can be considered as opposite ends of a bonding continuum, with polar covalent bonding lying between these two extremes.

The difference in electronegativities between bonded atoms gives an indication of the ionic character. The larger the difference in electronegativities between bonded atoms, the more polar the bond will be.

If the difference in electronegativities between bonded atoms is large, then the movement of bonding electrons from the element of lower electronegativity to the element of higher electronegativity is complete, resulting in the formation of ions.

Compounds formed between metals and non-metals are often, but not always, ionic.

Physical properties of a compound, such as its state at room temperature, melting point, boiling point, solubility, electrical conductivity, should be used to deduce the type of bonding and structure in the compound.

All molecular elements and compounds and monatomic elements condense and freeze at sufficiently low temperatures.

Some attractive forces must exist between the molecules or discrete atoms, for freezing to occur at sufficiently low temperatures.

Intermolecular forces acting between molecules are known as van der Waals forces.

There are several different types of van der Waals forces, such as London dispersion forces and permanent dipole-permanent dipole interactions — that includes hydrogen bonding.

London dispersion forces are forces of attraction that can operate between all atoms and molecules.

London dispersion forces are much weaker than all other types of bonding.

London dispersion forces are formed as a result of electrostatic attraction between temporary dipoles and induced dipoles caused by movement of electrons in atoms and molecules.

The strength of London dispersion forces is related to the number of electrons within an atom or molecule.

London dispersion forces get stronger as the number of electrons within an atom or molecule increases.