- Atoms that are stable have their outer orbits filled with electrons, where atoms that have only one electron in their outer orbit are unstable. Conversely, the unstable elements will combine to form complex molecules, where the stable elements will not combine at all.
- Covalent bonds occur when atoms share electrons to stabilize their outer electron orbits. One example is oxygen, which has four electrons in its outer orbit but can hold eight.
- Ionic bonds occur when one electron from an atom's outer orbit transfers to another element causing the first element to become positively charged (because they lost an electron) and the second element negatively charged (because they gained an electron). It's like when sodium and chlorine bond to form table salt.
- Metallic bonding is similar to covalent bonding in that electrons are shared among the atoms. The difference is they have one electron in their outer orbits but share them with many atoms, creating a very strong bond.
- Different atoms bond together in different formations based on the number of electrons they have in their outer orbits. Metals such as sodium form blocks. Nonmetals such as carbon form hexagons, which are flat, like in graphite, or stand up, like in diamonds.
