Video Transcript
Which of the diagrams shows the
ground state for an atom that contains two electrons?
Electrons in an atom occupy energy
levels. Energy levels are regions around
the nucleus in which electrons move according to their energies. The energy level closest to the
nucleus in an atom is the K energy level. The second energy level is the L
energy level. The third energy level is the M
energy level. And the fourth is the N energy
level. With this information, we can
eliminate answer choices (D) and (E) as the energy levels are not labeled
correctly. Let’s remove these answer choices
from the screen to finish discussing the question.
We are told that the atom in the
question is in the ground state. The ground state is the lowest
possible energy state of an atom. The ground state is achieved when
all of the electrons in an atom are in the lowest possible energy levels. Of the four energy levels shown,
the energy level with the lowest energy is energy level K. The energy levels increase in
energy the farther they are from the nucleus. So we should expect that for an
atom to be in the ground state, the electrons should fill the K energy level first,
followed by L then M then N.
We now know the order in which the
electrons will fill the energy levels. But we need to know how many
electrons each energy level can hold. The K energy level can contain a
maximum of two electrons. The L energy level can hold up to
eight, M up to 18, and N up to 32. The atom in the question, which is
in the ground state, contains two electrons. The first electron will occupy the
lowest energy level, level K. The second electron will also be
found in the K energy level, as this energy level can hold up to two electrons. So an atom that contains two
electrons will be in the ground state when both of those electrons occupy the K
energy level. This is represented by the diagram
shown in answer choice (C).
