# How is Zn not a transition metal? [duplicate]

A transition metal can be defined as an element that possesses an incomplete sub-level in one or more of its oxidization states. In the textbook I'm reading, it claims that zinc is not a transition metal because it has a full $$d$$-sub-level in all its oxidization states.

A quick google reveals that zinc has oxidization states $$-2, 0, +1$$, which means that zinc(with oxidization number $$+1$$) has an incomplete d-sub-level and is a transition metal.

What's going on here? Is my textbook incorrect?

• Zinc does not have an incomplete $d$ subshell, it does not use any of that subshell for valence orbitals and even its heats of fusion and vaporization betray a lack of typical transition-metal properties. It just does not fit. But hey, we still have scandium through copper in that period. – Oscar Lanzi Nov 21 at 3:03
• So is zinc just a special case? I would imagine cadmium should have these properties if not? – Sean Xie Nov 21 at 3:15
• Cadmium isn't a transition metal either. – Oscar Lanzi Nov 21 at 3:17

Zinc in the +1 oxidation state is $$\text{[Ar]}3d^{10}4s^1$$, and even in its highest, most common known oxidation state +2 (which the quoted values above seem to have forgotten) it's still $$\text{[Ar]}3d^{10}$$. No known zinc species in what we normally consider the realm of chemistry breaks that complete $$3d^{10}$$ subshell, and we would need a major revamp of our calculations and models if any ever does. Moreover, the thermophysical properties of zinc also betray a loss of transition-metal character. Zinc is just not a transition element.
As a followup to my question, I want to state $$\ce{Zn}$$ is not a transition metal also because of the Aufbau Principle. According to the principle, electrons are removed from the subshell with the highest quantum number first. So in a case such as $$\ce{Zn^2+}$$, electrons are moved from the $$4s$$ subshells instead of the $$d$$-subshells. The $$d$$-subshell remains full.