What is the main component of atoms that determines the type of bond that forms between atoms or compounds? explain.

I think There should be a valanced state in every atom. (Valanced state means, 8 electrons in the outer most orbit) In case take a atom has 8 electrons in the outer orbit, so when bonding the two atom to form a molecule, there is a Ionic Bond (because of both atoms has its own valanced electron(8 electrons in outer most orbit).

What are the following units