"In chemistry, the term transition metal (or transition element) has two possible meanings:The IUPAC definition defines a transition metal as \"an element whose atom has a partially filled d sub-shell, or which can give rise to cations with an incomplete d sub-shell\".Most scientists describe a \"transition metal\" as any element in the d-block of the periodic table, which includes groups 3 to 12 on the periodic table."@en .