Are electrons inside or outside the nucleus?
Electrons are always on the outside of the nucleus. They like to spin around in spherical orbits about the nucleus like a satellite travels around the earth.
When there are a higher number of electrons or electron orbits, they appear as an electron cloud around the nucleus. The nucleus itself consists of neutrons and protons forming a central core.
The protons in the nucleus, being like forces (all positive), generally try to get away from each other, but are held together by the atomic binding force.
The negative electrons are attracted to the positive nucleus. They and will stay in orbit around the nucleus unless another atom comes near enough to react with, or if an electric force causes them to move. Once an atom has completed its outer shell of electrons, it becomes stable and has less affinity to react.
There are some good illustrations here: