Electrons don't go around the nucleus in nice little round circular paths, but are found in
regions called

Orbitals

Explanation:

An orbital is a region in space where there is a high probability of finding an electron. An orbital is a probability function put forward by the wave mechanical model of the atom.

The wave mechanical model derives its principles from the Heisenberg uncertainty principle and the principle of wave particle duality.

Since we can not describe the momentum or position of the electron at any time with certainty, an orbital is a probability function that describes the region in space where the electron may be found around the nucleus.

a police officer and a ambulance

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).