Explain why electrons are described as negatively charged particles that orbit the nucleus in shells or energy levels.

Electrons carry a negative electric charge, equal in magnitude to the positive charge of a proton, and they are attracted to the positively charged nucleus. They are not fixed in place but move in defined regions called shells or energy levels, which are the only stable distances from the nucleus where they can exist. This arrangement allows atoms to maintain electrical neutrality when the number of electrons equals the number of protons.

The answer demonstrates understanding of electron charge, attraction to the nucleus, and the concept of shells/energy levels, directly addressing the learning objective.