Concepts

So in the last unit, there were some pretty confusing concepts, but one of the simplest was the idea of core and valence electrons, valence being the one that are directly involved with forming bonds, and core bonds being the bonds that are on the inside, and have an identical structure to the noble gas that last came before it. When bonding a chemical is trying to have a stable outer electron shell with 8 electrons, either shared or not, in it. It should be noted that ionic bonds are not part of this unit, because they are "simple" in comparison. This is because of the difference shown here:

In the bond on the left there is a sharing of electrons, while on the right there is an ionic bond.Think of it like the electron is a business, they both need to have eight employees, but there are 14 in all, so if two employees work at both businesses there is no problem at all. In an ionic bond one of the businesses would just be underemployed. THIS video will go over the two in more depth. This picture shows the electron exchange of fluorine:

In short this unit is over the sharing of electrons between atoms, resulting in complex chemicals such as water and acids. Crash Course goes over bonds HERE.