late 14c., "fill with disease, render pestilential; pollute, contaminate; to corrupt morally," from Latin infectus, past participle of inficere "to stain, tinge, dye," also "to corrupt, stain, spoil," literally "to put in to, dip into," from in- "in" (from PIE root *en "in") + facere "to make, do, perform" (from PIE root *dhe- "to set, put").
Between a cation, which is usually a metal, and an anion, which is usually a nonmetal. A covalent bond involves a pair of electrons being shared between atoms.
