Monovalent ion, an atom, ion, or chemical group with a valence of one, which thus can form one covalent bond. An atom having just one covalent bond. In this molecule the hydrogen atom and chlorine atoms are monovalent. Valency is actually the capability measurement of an element to form a chemical compound while reacting with another element. Similarly, when an element or ion gets a valency of 2, then it is known as the divalent element. For example Mg²+ os a divalent element. A trivalent element has three electrons in its valence shell. The nitrogen atom is a trivalent element.