# Question Video: Calculating the Number of Electrons That Must Be Lost for an Atom to Gain a Full Outer Shell Using Its Electronic Configuration Science

The energy level diagram shows the electronic configuration for an atom. How many electrons does the atom need to lose in order to gain a full outer shell?

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### Video Transcript

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 partially filled.

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.