An atom is the smallest part of an element that has the same properties as the element. All atoms in a particular element are the same.
All matter is made up of atoms, earning it the name the "building block" of matter. While atoms are the smallest part to possess the element's characteristics, atoms are made up of smaller parts called electrons, neutrons and protons. Protons carry a positive charge, while electrons carry a negative one. Neutrons are neutral. Protons and neutrons are about the same size, but electrons are considerably smaller. All elements have the same number of protons in the nucleus of each atom.