Transition Metals Learning Path

Definition and periodic-table classification

In chemistry, a transition metal is defined primarily by its position on the periodic table: it is an element in the d-block, corresponding to groups 3 to 12 (with some variations in practice). The IUPAC 2011 Principles of Chemical Nomenclature describe a transition metal as any element in groups 3–12, which matches the d-block elements. In practice, the lanthanides and actinides (f-block) are often treated separately as “inner transition metals,” though some sources may still consider them transition metals. Classification can vary for certain borderline cases. Group 12 elements (Zn, Cd, Hg) are sometimes excluded because their d subshell is filled (d10), meaning they do not show the same typical behavior associated with partially filled d subshells; however, they are often included for convenience in discussions of transition-element chemistry. The placement of group 3 elements (Sc/Y vs La/Ac vs Lu/Lr) also shows variation across periodic-table formats, with updated IUPAC-supported arrangements favoring Lu and Lr in group 3 to preserve atomic-number order and the correct f-block width. Transition metals are further described as “early” or “late” depending on which d-block groups they occupy, and some heavier group 2 elements (e.g., Ca, Sr, Ba) are sometimes called “honorary” transition metals due to d-orbital participation in bonding.

0/2 modes complete

d-Block versus inner transition metals

0/2 modes complete