An atom contains a nucleus.

The statement "an atom contains a nucleus" is true. The nucleus is the central core of an atom that contains protons and neutrons. The protons have a positive charge, while the neutrons have no charge. Electrons, which have a negative charge, orbit around the nucleus in specific energy levels or shells. The nucleus, being positively charged, holds the electrons in place through the electrostatic attraction between opposite charges. It is this arrangement of a central nucleus and orbiting electrons that forms the basic structure of an atom.