Greeks

• The word "atom" is derived from the Greek language.Image by Flickr.com, courtesy of Herm¨¦s
  
  The word atom is derived from the Greek language which means uncuttable or indivisible. To put it simply, something that can't be separated any more.
  
  

Three Types of Particles

• Atoms are composed of three types of particles: protons, neutron, and electrons.
  
  

Protons and Neutrons

• The atomic nucleus is composed of protons and neutrons. These two make up most of the atom's atomic mass or atomic weight. Protons carry a positive electrical charge and neutrons have no charge. Therefore, neutrons are considered neutral.
  
  

Electrons

• Electrons have a negative electrical charge and surround the atomic nucleus at different levels or orbitals. These orbitals are similar to how planets encircle the sun.
  
  

Equal Quantity

• Atoms that contain an equal number of protons and electrons are considered electrically neutral.
  
  

Classification

• Atoms are classified by the number of protons and neutron in its nucleus. The quantity of protons determines the chemical element and the amount of neutrons determine the isotope of the element.