5. Atomic Structure

Charge, Mass, Location of P/E/N
  • Proton: +1, 1, nucleus
  • Electron: -1, 1/1836, shells
  • Neutron: 0, 1, nucleus

Definitions
  • Proton number / Atomic number: The number of protons in an atom.
  • Nucleon number:  The number of protons and neutrons in the nucleus of an atom.
  • Isotopes: Isotopes are atoms of the same element with the same number of protons but different number of neutrons.
  • Relative atomic mass (Ar): The average mass of an atom compared to the mass of 1/12 of the mass of a carbon-12 atom.
Note: Ar of chlorine (35.5)  is not a whole number because chlorine atoms exist in the form of 2 isotopes in different proportions. Ar of chlorine is the average mass of the isotopes.