Definition;
- A transition element has at least one ion with an incomplete d sub-shell.
Zinc and Scandium are not transition elements as they do not fit the definition. They are known as d-block elements
Zinc - 1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^2 Scandium - 1s^2 2s^2 2p^6 3s^2 3p^6 3d^1 4s^2
Zinc forms an ion that is Zn^2+, this means that the electrons are taken from the 4s^2 subshell leaving Zinc with an unchanged full d-subshell. Transition elements/metals should have an incomplete subshell so zinc is not a transition element but instead a d-block element. Zn^2+ = 1s^2 2s^2 2p^6 3s^2 3p^6 3d^10
Scandium forms an ion that is Sc^3+. It firstly looses the 2 electrons from the 4s^2 subshell followed by the only electron in the 3d^1. Scandium is now left with an electron confinguration with no electrons in the d-subshell, this again doesnt fit the definition of transition element so scandium is not a transtion element but a d-block element. Sc^3+= 1s^2 2s^2 2p^6 3s^2 3p^6
Remember, if a d-block element has a white compound in that oxidative state then it would probably have a full d-subshell or an empty d-subshell.
The transition elements form positive ions as they are metals. This means that when an ion is formed, electrons are removed from the atom. 4s electrons are removed first.
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