iÂ·onÂ·ic bond. A chemical bond formed between two ions with opposite charges. Ionic bonds form when one atom gives up one or more electrons to another atom. These bonds can form between a pair of atoms or between molecules and are the type of bond found in salts.
The answer is supernovae. In a supernova explosion, neutron capture reactions take place (this is not fusion), leading to the formation of heavy elements. This is the reason why it is said that most of the stuff that we see around us come from stars and supernovae (the heavy elements part).
Our bodies form lactic acid naturally. It forms as the body converts carbohydrates into energy during periods of low oxygen levels, which can occur with intense physical exercise. In foods, lactic acid either occurs naturally, or a synthesized form is added as a flavoring or preservative agent.