What are the principles of covalent and ionic bonds?

[LogicalAcid]

I have gotten the principles of them down, but I still have some more detail to cover. From what I know about Ionic bonds is the following.
-When an atom reacts with another atom in order to gain a full valence shell, the atom can either lose and electron, or gain one depending on the number of Valence e- it has until a full shell, or an empty shell (therefore making the shell "below'' it the valence shell (which may or may not have a full shell). So once it reacts, if It loses an electron, it forms a positively charged Ion, if it gains one, it becomes a negatively charged Ion. The atom it reacted with may become a Positive Ion, or negative, always the opposite of the atom that reacted with it though. Now that there is both a + ion and a - ion , electrostatic forces cause the two charges to attract therefore forming an ionic bond.

Correct me if need be.

 

[Borek]

More or less you are on the right track, although it doesn't have to be one electron (it can be more than one) and in the case of transition metals it becomes much more complicated.

Note: thread title is "covalent and ionic bonds". Be aware that while we can classify bonds as such or such they always are a mix of both types, sometimes nicely dominated by one type (like in NaCl or CH₄), but sometimes they are quite difficult to classify.