Two atoms can "react" chemically in either of two ways. In the ionic reaction, one can give up an electron (becoming a positive ion or cation [so called because it is attracted to an electric cathode]) to the other, which becomes a negative ion or anion [because it is attracted to an electric anode]; the two oppositely charged ions are then attracted to each other by the Coulomb interaction but do not have to stay together - sort of like today's high school dances. When the two atoms can't decide which would rather be the donor or the receptor of electrons, they can form the ambiguous or covalent bond, in which they share one or more electrons; in this case everyone stays electrically neutral but no drifting away from one's partner is allowed.