The term nonmetal (chemistry) is also used for those elements which are not metallic in their normal ground state; compounds are sometimes excluded from consideration. Some textbooks use the term nonmetallic elements such as the Chemistry of the Non-Metals by Ralf Steudel, which also uses the general definition in terms of conduction and the Fermi level. The approach based upon the elements is often used in teaching to help students understand the periodic table of elements, although it is a teaching oversimplification. Those elements towards the top right of the periodic table are nonmetals, those towards the center (transition metal and lanthanide) and the left are metallic. An intermediate designation metalloid is used for some elements.