Protons, neutrons, and electrons ; SCIENCE

• Protons - found INSIDE the nucleus carries the POSITIVE charge
• 1886 - Eugen Goldstein (1850-1930) discovered evidence for the existence of this positively charged particle
• Electrons - found OUTSIDE the nucleus carries NEGATIVE charge
• 1897 - J.J Thomson discovered the first subatomic particle, the electron
• Neutron - found INSIDE the nucleus of an ATOM
• 1932 - Chadwick proved the existence of neutrons - elementary particles devoid of any electrical charge
• Atomic number - number of protons which equals to the number of electrons
• Mass number - sum of the number of protons and neutrons in an ATOM