What particles are most atoms composed of?

Most atoms are composed of protons, neutrons, and electrons. Protons and neutrons form the nucleus of the atom, contributing to most of the atom's mass, while electrons orbit the nucleus in various energy levels. This arrangement is fundamental to the structure of matter, as protons determine the atomic number and identity of the element, while electrons play a crucial role in chemical behavior and interactions with other atoms. The presence of these three types of particles is what defines the atom as a whole and is critical to understanding atomic theory and chemistry.