There are many different types of chemical bonds. Molecules and atoms that have a positive or negative charge are called ions. When cations or anions come together, they form ionic bonds, such as sodium chloride, or the main compound in normal saline. Ions are vital to maintaining homeostasis within the body. In covalent bonds, atoms and molecules share electrons. In a nonpolar covalent bond, they are shared equally. For example, carbon atoms use covalent bonds to create the stable framework of the large molecules that make up most of the structures of the human body. In polar covalent bonds, those electrons are shared unequally, creating a slightly charged compound or molecule, such as water, which has the unique property of being attracted to itself. This chemistry allows our bodies to complete the complex physiological functions, which is a foundation for all biology.