Chelation
Chelation refers to the bonding of elemental atoms that cannot normally be bonded. For example, Sodium is a metal element that can bond with many other elements, like chlorine (forming common table salt: NaCl), or hydrogen and oxygen (Sodium hydroxide). The reason for this is that the way that atoms bond with each other is similar to a jigsaw puzzle: Only the proper shape can fit into the empty space made by the other pieces. However, with atoms, it's a bit different. For each element, the atom carries a certain number of electrons in orbit around its nucleus. Sometimes these orbits are split into levels, and only a certain number of electrons can fill each orbit before moving to a higher orbit.