Why don't we fall through the floor?

Because your electrons repel other electrons. For example: the reason you don't fall through your chair when sitting on it is because your electrons from the atoms in your body repel off the chairs atoms. Fun fact: you technically have never touched anything since the electrons repel other electrons, which means we're all floating in mid air because of our electrons repel off of others!

boi ... We got structure and support such as beams and things holding us up.