since atoms are mostly empty space, why don't we fall through a floor we stand on?

an atom is a very tiny entity, it has a diameter of 10^-12cm ,a fullstop mark on this page is billionth times larger than an atom and matters made up of this atoms are not left loose, they are held by a strong force of attraction which could be either ionic, metallic, dative, covalent or hydrogen bonding etc.  Therefore atoms in the floor of your building is not loose but held by a strong force, this is why it didn’t fall.