What are the main components of an atom?

The main components of an atom are protons, neutrons, and electrons. Protons are positively charged particles found in the nucleus of an atom, contributing to its overall mass and determining the element's identity. Neutrons, which have no charge, also reside in the nucleus and add to the mass of the atom but do not affect its chemical properties. Electrons are negatively charged particles that orbit the nucleus in various energy levels and are primarily responsible for the atom's chemical behavior and bonding with other atoms.

This understanding of atomic structure is fundamental to chemistry and physics. The other options mention components or terms that do not accurately describe the basic structure of an atom. For example, nuclei are assemblies of protons and neutrons but not a fundamental component on their own. Photons, while relevant in discussions of light and electromagnetic radiation, are not part of atomic structure. Quarks are subatomic particles that make up protons and neutrons but are not components of the atom itself at the atomic level. Ions refer to charged atoms that have gained or lost electrons but do not represent the basic constituents of an atom. Isotopes involve variations in neutrons within a single element rather than being a component of an atom. Thus, the correct choice