Why are d-block elements are called outer transition elements?
Ulex says d-block elements can be referred to as outer transition elements, though the expression is not in common use. This is to contrast them with the f-block elements which are sometimes called ‘inner transition elements’. For a series of outer transition elements the electrons are added to d orbitals from one element to the next. In period 6 from lanthanum, then lutetium to mercury the electrons go into the 5d shell. For inner transition elements the electrons go into f orbitals. So in period 6 from cerium to ytterbium the electrons are added to the 4f shell. That is two shells in from the outer electrons in the 6s orbital. Risk assessment Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on w
