Most of the compounds found in living things contain carbon, hydrogen, nitrogen, or hydrogen atoms. A group of other elements, including sulfur, magnesium, and iron, make up less than 1% of the atoms in most living systems. Trace elements, such as copper, zinc, chromium, and even arsenic, although necessary for biological function, only make up a minute portion of an organism, less than 0.01% of all atoms. Due to their complexity and impact on their behavior in cooking, let’s talk a little bit more about the bonds that connect atoms together.
There are two types of bonds that connect two atoms to yield a molecule or compound: ionic and covalent. Ionic bonds form between atoms that have opposite charge due to the loss or gain of electrons. Atoms that have become charged have their own name—ions. Ionic bonds form when an ion with a positive charge (a cation) is bonded to an ion with a negative charge (an anion).
The resulting molecule is called an ionic compound or a salt. This terminology is apropos because the salt that you sprinkle on your popcorn, NaCl, is an ionic compound consisting of a positively charge sodium atom or ion (Na+) and a negatively charged chlorine atom or ion (Cl−)