What are the primary types of chemical bonds?

The two primary types of chemical bonds are covalent bonds and ionic bonds. 

Covalent Bonds

A covalent bond is formed when two atoms share a pair of valence electrons. After forming a covalent bond, the pair of electrons shared by the two atoms extend around the nuclei of the atoms, creating a molecule. Covalent bonds may be polar or nonpolar in nature. In polar covalent bonding, the electrons are shared unequally, generating a difference in charge, where one end of the newly formed molecule has a negative charge and the other end has a positive charge. This type of chemical bond usually happens between two nonmetal atoms. Polymers are an example of a compound that has covalent bonding. 

Ionic Bonds

An ionic bond involves a transfer of electrons from one atom or molecule to another. It is formed when one atom donates one or more of its valence electrons and another atom accepts these electrons. With this type of electron transfer, one of the atoms develops a positive charge and is called the cation, while the other develops a negative charge and is called an anion. Ionic bonds derive their strength from the difference in charge between the two atoms. The greater the difference in charge between the anion and the cation, the stronger the ionic bond will be. This type of chemical bond occurs strictly between metal and nonmetal atoms. Sodium Chloride (NaCl) is a common example of an ionic bond.