Video Transcript
Which of the following statements
accurately describes a paramagnetic substance? (A) It is a substance that is
attracted to an external magnetic field because all electrons are paired in its
orbitals. (B) It is a substance that repels
an external magnetic field due to the presence of unpaired electrons in its
orbitals. (C) It is a substance that is
attracted to an external magnetic field due to the presence of unpaired electrons in
its orbitals. (D) It is a substance that repels
an external magnetic field, because all electrons are paired in its orbitals.
As its name suggests, a
paramagnetic substance is attracted to a magnetic field. On the other hand, a diamagnetic
substance weakly repels a magnetic field. Examining the electronic
configuration of a metal could help us to predict if the metal is paramagnetic or
diamagnetic. Let’s clear some space to look at
the electronic configurations of some of the metals found in period four on the
periodic table. The first nine elements listed are
the period-four transition metals. Zinc is not a transition metal, but
we will look at its electronic configuration in this video.
Now let’s look at how electrons are
organized in the valence shell orbitals. We can see that the number of
unpaired electrons increases across the first four transition metals. The number of unpaired electrons
then decreases until we reach zinc, which has no unpaired electrons in its valence
shell. Scandium, titanium, vanadium, and
manganese are paramagnetic. In contrast, copper and zinc are
diamagnetic. One contributing factor to this
difference is the presence of unpaired electrons.
Paramagnetic substances have at
least one unpaired electron. These unpaired electrons give the
atoms of the substance magnetic dipoles, allowing the substance to be attracted to
magnetic fields. In contrast, diamagnetic substances
generally have only paired electrons in their orbitals. So their atoms do not have magnetic
dipoles. This causes them to weakly repel
magnetic fields.
Now, if we look closely at the
electronic configuration of copper, we notice that it has an unpaired electron in
the 4s subshell. So, we would predict that copper
should be paramagnetic, when in fact it is diamagnetic. There are other types of magnetism
possible. For example, iron, cobalt, and
nickel are ferromagnetic, and chromium is antiferromagnetic. Now let’s take a look at the answer
choices again.
We can see that the statement that
most accurately describes a paramagnetic substance is statement (C). It is a substance that is attracted
to an external magnetic field due to the presence of unpaired electrons in its
orbitals.
