The Transition Metals and Electron Configurations

Introduction

Electron configurations give us a way to explore how electrons are arranged in atoms and ions. However, they also allow us to analyze the transition metals to a new level, as we can predict cations formed by them the most readily based on their electron configurations. Recall that the most stable sublevels are either completely empty, completely full, or exactly half-full with one electron in each orbital. Teachers can use this article to reinforce why electron configurations are useful and the fundamentals of quantum mechanics. 

Most transition metals are multivalent, meaning they form multiple stable cations. All of the alkali and alkaline earth metals only have one stable cation.

Scandium

We look at Scandium because it is the first transition metal in the periodic table. Its noble gas configuration is

$$[Ar]4s^23d^1$$

The \(3d\) sublevel is not empty, half-full, or completely full. The easiest way to get it to one of those states is to remove the one electron from it, giving the more stable \(Sc^{+}\). Its noble gas configuration is

$$[Ar]4s^2$$,

the same as a calcium atom. While the \(Sc^{+}\) can theoretically exist by this logic, the removal of two additional electrons will make the scandium ion.

A couple other things to note:

• These trends are not perfect; there are some exceptions, especially with the elements in the higher periods, which have been studied less thorouhgly.
• Cations with charges above +8 do not generally exist. A few transition metals can, however, form +8 cations.
• Multivalent atoms can thus form ionic compounds with anions in different ratios. For example, copper forms both \(+1\) and \(+2\) cations, so \(CuOH\) and \(Cu(OH)_2\) both exist.