The electrochemical series, also called the electromotive series, is a sequence of elements (chiefly metals) listed in order of their standard redox potentials – i.e., the potential developed by an electrode of the element immersed in a molar solution (see mole) of one of its salts (see electrochemistry). The series starts with the metal that tends to lose the most electrons in reactions. A standard hydrogen electrode is arbitrarily assigned an oxidation potential of zero, so that the metals can be compared. Those that lose electrons more readily than hydrogen are termed electropositive; those that lose electrons less readily are called electronegative (see electronegativity). Metals high in the series are generally more reactive than those lower down, and displace them from aqueous solutions of their salts. The order of some common metals in the electromotive series is: lithium, potassium, calcium, sodium, magnesium, aluminum, zinc, chromium, iron, cobalt, nickel, tin, lead, hydrogen, copper, mercury, silver, platinum, and gold. See also ionization potential.