### Video Transcript

What is the maximum number of
electrons that can occupy energy level X shown in the diagram?

Energy levels are regions around
the nucleus in which electrons move according to their energies. The energy levels each have a
different energy. The energy level closest to the
nucleus has the lowest energy. And the energy increases as the
energy levels get farther from the nucleus.

In addition to having a different
energy, each energy level can hold a different maximum number of electrons. For energy levels one through four,
we can calculate the maximum number of electrons each can contain using the equation
two 𝑛 squared. 𝑛 in this equation represents the
energy level.

To answer the question, we need to
determine the maximum number of electrons that the energy level marked X can
contain. The X energy level is energy level
number three. So we can substitute three for 𝑛
in the equation. Three squared is nine, and two
times nine is 18. So the maximum number of electrons
that can occupy energy level X in the diagram is 18 electrons.