Video Transcript
Which element in the fourth period
of the periodic table and in the d block is not a transition metal when considering
its electronic configuration? (A) Chromium, (B) scandium, (C)
copper, (D) zinc, (E) iron.
Firstly, a transition element is an
element that has atoms with incomplete d subshells or can give rise to cations with
incomplete d subshells. The periodic table can be divided
into blocks, which represent the various electron subshells found in atoms. There are s, p, d, and f subshells,
and this letter tells us what type of atomic orbitals the subshell contains. Each subshell has a maximum amount
of electrons that it can hold. We can see that d subshells can
hold a maximum of 10 electrons.
The d block elements in period four
are found in groups three through 12. We can see that all the elements
listed in the answer choices are d block elements. However, to be classified as a
transition element, the d subshell of the atoms or ions must contain less than 10
electrons.
Now, let’s move across period four
and look at the electronic configuration of each element to see if it meets the
definition of a transition element.
Let’s begin with scandium. Scandium has the electronic
configuration brackets Ar 4s2 3d1. Since scandium has only one
electron in its d subshell, it has an incomplete d subshell and must be a transition
metal. Therefore, we can eliminate answer
choice (B).
Now, let’s consider chromium. Chromium has the electronic
configuration brackets Ar 4s1 3d5. Since chromium has five electrons
in its d subshell, it also has an incomplete d subshell and must be a transition
metal. Therefore, we can eliminate answer
choice (A).
Now, let’s consider iron. The electronic configuration of
iron is brackets Ar 4s2 3d6. Because iron only has six electrons
in its d subshell, it has an incomplete d subshell and is a transition metal. This means we can eliminate answer
choice (E).
Moving on to copper, we see that
its electronic configuration is brackets Ar 4s1 3d10. Because copper has 10 electrons in
its d subshell, we might think that it is not a transition metal, since the d
subshell is complete. However, copper atoms can form
copper two plus cations, which have incomplete d subshells. Therefore, copper is a transition
metal, and we can eliminate answer choice (C).
Finally, the electronic
configuration of zinc is brackets Ar 4s2 3d10. We can see that zinc atoms have
complete d subshells. Zinc only forms Zn2+ cations, which
have the electronic configuration brackets Ar 3d10. So the d subshells of zinc cations
are also complete. Therefore, zinc cannot be
classified as a transition metal.
In conclusion, the period four d
block element that is not a transition metal when considering its electronic
configuration is zinc, or answer choice (D).
