Video Transcript
Given the data of successive
ionization energies, shown in the table, what is the likely identity of transition
metal X? (A) Manganese, (B) scandium, (C)
vanadium, (D) titanium, or (E) chromium.
Our question gives us a table of
successive ionization energies and asks us to identify a transition metal from the
data. To do this, we need to understand
that successive ionization energies quantify how much energy is needed to
consecutively remove electrons from one gaseous-state element. In other words, our table of
successive ionization energies tells us how much energy per mole it would take to
remove the first seven electrons consecutively from our unknown element, turning it
into an increasingly positive ion.
Typically, the amounts of energy
required to remove electrons from the outermost shell are lower than the amounts of
energy required to remove the core electrons. Therefore, we are looking for a
drastic increase in ionization energy. This will signify that the
electrons now being removed are closer to the nucleus. So we can see at what point all
valence electrons have been removed.
If we look closely, the energy
required between the fifth and sixth electrons seems to jump much higher than the
previous increases. So, this indicates that there are
five valence electrons in our element and the remaining two are core electrons. Now, since we know that our element
is a transition metal, we can use the periodic table to find a transition metal that
has five valence electrons.
Recall that the periodic table
displays elements by increasing atomic number. Therefore, to quickly count the
number of valence electrons, we can use the nearest noble gas, argon, which has an
atomic number of 18 and therefore 18 electrons and a full outer shell. Starting then on the next row with
period four, the first two valence electrons account for potassium and calcium. And then, we can continue to count
upwards from the left to determine the number of valence electrons.
So, if we start from the left side
with the nearest transition metal, scandium, we see that it has three valence
electrons. Titanium has four valence
electrons. Vanadium would then have five
valence electrons. We can therefore determine that the
likely identity of transition metal X is (C), vanadium.
