A Higgs-Boson particle.
Atoms are NOT the smallest particle- they are the smallest COMPLETE particle. In an atomic reaction, the atoms are broken apart, and release energy.
The atom is the smallest known particle.
The smallest particle of an element is called an atom.
The smallest particle in the atom is the electron.
This particle is the atom.
An atom is the smallest particle of a substance.
An atom is a particle, the smallest particle that can exist by itself.
An atom is smallest particle there is and it cannot be broken down any more.
The smallest particle that can ever be found, it cannot be broken down in to anything smaller
An iron atom is the smallest iron particle that still has the properties of iron.
An ATOM!!!! An atom can be sub-divided in to protons, neutrons, and electrons.
An atom is the smallest particle of an element that can be uniquely identified as that specific element.Note that this question is different from asking "What is the smallest particle in an atom?" (see related question below). Atoms are composed of smaller particles (protons, electrons, and neutrons), but the smallest thing that has the identity of a specific element is the atom.The smallest particle of an element that still retains all that element's properties is called an ATOM.