Humber Admissions Practice Test

The nucleus is the central part of an atom and is composed of protons and neutrons. While protons carry a positive charge, neutrons are neutral, meaning they have no electrical charge. This unique characteristic of neutrons is essential for the stability of the atom. It is in the nucleus that the majority of the atom's mass is concentrated, specifically due to the presence of these protons and neutrons.

Orbital shells refer to the regions surrounding the nucleus where electrons are likely to be found, but they do not contain neutrons. The mass number represents the total number of protons and neutrons in the nucleus but does not specifically indicate the presence of neutral particles. The electron cloud is a term used to describe the area around the nucleus where electrons are located, which again does not contain neutrons. Therefore, the nucleus is the part of the atom that specifically includes the neutral charged particles, making it the correct answer.