The atom is the smallest object that retains the properties of an element.
Atoms are composed of electrons and a nucleus. The nucleus contains protons and neutrons.
All atoms are electrically neutral, because every atom has an equal number of electrons and protons.
Nearly all of the atom's mass is located in the nucleus. The nucleus is tiny compared with the total size of the atom.
Most of the atom's volume holds the electron cloud, whose mass is tiny.
Atoms are generally spherical, although there are indications that atoms of the very heaviest elements may exist as squashed spherical shapes.
An atom's chemical behavior is determined by the arrangement of its electrons.
Atoms may combine with one another by chemical bonding to produce molecules. They may also ionize to form ionic compounds.