To put it simply, ionic bonds form when one atom transfers an electron to another atom. The atom that gains an electron becomes a negative ion while the atom that loses an electron becomes a positive ion. Covalent bonds form when two atoms share electrons. A hydrogen bond is when you have a negatively charged O, N, or F atom in one molecule, a positively charged H atom latched on to an O, N or F atom in another molecule. An example of a hydrogen bond is water.
