On what ground can you say that scandium (Z = 21) is a transition element but zinc (Z = 30) is not ?

Explanation

Scandium (Z = 21) atom contains incompletely filled 3d - orbital `(3d^(1))` in its ground state and hence, is a transition element. On the other hand, zinc (Z = 30) contains completely filled 3d - orbital in its atomic state `(3d^(10)4s^(2))` and also in the stable oxidation state `(Zn^(2+), 3d^(10))`. So it is not considered as a transition element.