A compound can either be covalent or ionic in nature. Covalent compounds are formed when two or more non-metal atoms share their electrons to form a molecule. For example, when two hydrogen atoms and one oxygen atom come together, they share their electrons to form a molecule of water (H2O). In contrast, ionic compounds are formed when a metal atom and a non-metal atoms transfer their electrons, with the metal atom giving up electrons and the non-metal atom accepting them. This results in the formation of positively charged ions (cations) and negatively charged ions (anions), which are held together by electrostatic attraction. Examples of ionic compounds include sodium chloride (NaCl) and potassium iodide (KI).