atomic and mass numbers

• Atomic number


  The number of protons in an atom
• Mass number


  The total number of protons and neutrons in an atom
• Calculating the number of neutrons


  Subtract the atomic number from the mass number
• Atoms


  • Contain a central nucleus with protons and neutrons
  • Have electrons orbiting the nucleus
  • Have no overall charge because the number of electrons equals the number of protons
• Isotope


  Atoms of the same element with different numbers of neutrons
• Ion


  An atom that has lost or gained one or more electrons, giving it an overall positive or negative charge
• Atoms can lose electrons from their outer energy level to form positive ions
• If an atom loses one electron, the ion has a +1 charge
• If an atom loses two electrons, the ion has a +2 charge