Yes, there are particles smaller than an atom. Atoms are composed of subatomic particles, namely protons, neutrons, and electrons. However, within the realm of particle physics, smaller particles are known to exist. Here are a few examples:
Quarks: Quarks are elementary particles and are considered the fundamental building blocks of protons and neutrons. They are never observed in isolation but are always found bound together in combinations called hadrons.
Leptons: Leptons are another class of elementary particles that include electrons, muons, and taus, along with their corresponding neutrinos. Electrons are the most familiar leptons and are responsible for electrical conduction in many materials.
Gauge Bosons: Gauge bosons are particles that mediate the fundamental forces of nature. For example, photons are the gauge bosons of the electromagnetic force, while W and Z bosons are responsible for the weak nuclear force. Gluons mediate the strong nuclear force.
Higgs Boson: The Higgs boson is an elementary particle discovered at the Large Hadron Collider (LHC) in 2012. It interacts with other particles, providing them with mass.
These are just a few examples, and the field of particle physics continues to explore and discover smaller particles and fundamental constituents of matter. It's worth noting that the particles mentioned above are point-like, meaning they have no known internal structure or size. Instead, they are considered to be fundamental and indivisible entities.