How does the energy of an electron change when the electron moves closer to the nucleus?

a. It doubles.

b. It increases.

c. It decreases.

d. It stays the same.

C. It decreases

As the electron moves closer to the nucleus, its energy decreases as energy levels of the electron closer to the nucleus are of lower energy, as electrons are attracted to the nucleus (because the nucleus is positively charged) and the closer the electron is to the nucleus, more external work has to be put in to move the electron farther away, hence the electron is of lower energy.