What is the fundamental difference between covalent and ionic bonding? in a covalent bond, the partners share a pair of electrons; in an ionic bond, one partner accepts electrons from the other. in covalent bonding, both partners end up with filled outer electron shells; in ionic bonding, one partner does and the other does not. covalent bonding involves only the outermost electron shell; ionic bonding also involves the next electron shell inside the outermost shell. covalent bonds form between atoms of the same element; ionic bonds form between atoms of different elements?