Video Transcript
According to the successive
ionization energies of element X shown in the table below, which group in the
periodic table does element X belong to? (A) Group one, (B) group two, (C)
group three, or (D) group four.
In this question, we need to
identify the periodic table group of element X using its successive ionization
energies.
We can begin by defining the first
ionization energy, which is the amount of energy needed for displacing the most
loosely bound electron from an isolated gaseous atom. This equation represents the first
ionization energy for a boron atom. We can see that this process
generates a boron one plus cation and one electron for a set amount of energy. We can represent the second and
third ionization energies with similar equations. During the second ionization energy
event, a boron one plus cation loses a single electron. A boron two plus cation loses
another electron during the third ionization event.
We can use these equations to
understand the meaning of successive ionization energies. They are the amounts of energy
needed for consecutively displacing electrons from one gaseous state element. While these first three ionization
energies do increase, they are not drastically different. This is because these first three
electrons removed are in the same outermost electron shell. Ionization energy values are
related to the electron shell the electron being removed occupies and its distance
from the nucleus.
Valence electrons, which are
farthest from the nucleus, are relatively easy to remove. Core electrons are closer to the
nucleus and therefore have a stronger attraction to it and require much more energy
to remove. As these first three valence
electrons removed were in the same electron shell, they were of similar distance
away from the nucleus.
Let’s now have a look at the fourth
ionization energy event for boron. At 25026 kilojoules per mole, the
fourth ionization energy value is drastically different from the first three. This is because the fourth electron
removed is a core electron and is much closer to the nucleus. Thus, more energy is required to
displace it. The pattern of successive
ionization energy values reveals details about an element’s electronic configuration
and thus its place on the periodic table.
Let’s have a look at the table of
ionization energies for element X to determine in which periodic table group it
resides. The first three ionization energy
values of element X increase but are not drastically different. There is a strikingly large
increase from the third to the fourth ionization energy value. This suggests that the fourth
electron removed from element X is in a core electron shell. It is likely then that element X
has three valence electrons and resides in group three or 13 of the periodic
table.
Therefore, the group in the
periodic table that element X belongs to is answer choice (C), group three.
