What does the nucleus of an atom contain?

The nucleus of an atom is composed of protons and neutrons. Protons are positively charged particles that determine the atomic number of an element, which in turn defines its identity. Neutrons are neutral particles that contribute to the atomic mass and stability of the nucleus. The presence of both protons and neutrons within the nucleus is essential for understanding the structure of an atom, as they collectively make up the bulk of an atom's mass.

In contrast, electrons, which are negatively charged particles, orbit around the nucleus in energy levels or shells and are not found in the nucleus itself. Therefore, while electrons play a crucial role in interactions and bonding between atoms, they do not contribute to the composition of the nucleus. Hence, the accurate understanding of atomic structure highlights that the nucleus strictly consists of protons and neutrons.