In the 1920s, scientists decided that electrons do not orbit the nucleus like planets. Rather, they believed that electrons could be anywhere in a cloud-like region around the nucleus.

In this new model, the specific orbits have evolved into levels where electrons with the same amount of energy are found.

For instance, the lowest-energy electrons are in an energy level near the nucleus that can hold only 2 electrons. Higher-energy electrons are in larger energy levels farther from the nucleus. These larger energy levels can hold 8 or more electrons.