The energy level diagram below
shows the electronic configuration for an atom. How many electrons does the atom
need to lose in order to gain a full outer shell? (A) One, (B) two, (C) three, (D)
four, or (E) six.
The question tells us that the
given diagram is an energy level diagram. Energy levels are distances from
the nucleus that describe the location of electrons. As shown in the energy level
diagram, the energy levels are K, L, M, and N. K is the first energy level and is
filled first. L, M, and N are the second, third,
and fourth energy levels, respectively.
Each energy level has a different
maximum number of electrons. If an atom has the maximum number
of electrons in its outer shell, it is said to have a full outer shell. K is two, L is eight, M is 18, and
N is 32. We can see how electrons fill
energy levels by using the electronic configuration.
Electronic configuration is defined
as the distribution of electrons in energy levels. The electronic configuration for
this atom is 2,2. This tells us that there are two
electrons in energy level K. As the maximum number of electrons
in energy level K is two, we can tell that this shell is full. There are also two electrons in
energy level L. But in this case, the maximum
number of electrons is eight. Therefore, energy level L is
The question asks how many
electrons does the atom need to lose to gain a full outer shell. As K is the only full shell, we
have to figure out how many electrons need to be lost so that only K is full. We can see that two electrons must
be lost. When these electrons are lost, the
atom has the same electron configuration as the closest noble gas, helium.
Thus, the number of electrons that
the atom needs to lose in order to gain a full outer shell is (B), two.