atomic number and mass number

• Atomic number

  The number of protons in the nucleus of an atom
• Mass number

  The total number of protons and neutrons in the nucleus of an atom
• Atoms have no overall charge because the number of electrons is the same as the number of protons
• Lithium

  • 3 protons
  • 3 electrons
  • 4 neutrons
• Boron

  • 4 protons
  • 4 electrons
  • 5 neutrons
• Sodium

  • 11 protons
  • 11 electrons
  • 12 neutrons
• Fluorine

  • 9 protons
  • 9 electrons
  • 10 neutrons
• Phosphorus

  • 15 protons
  • 15 electrons
  • 16 neutrons
• Isotopes

  Atoms of the same element with different numbers of neutrons
• Carbon isotopes

  • 6 protons, 6 neutrons
  • 6 protons, 7 neutrons
  • 6 protons, 8 neutrons
• Chlorine isotopes

  • 17 protons, 18 neutrons
  • 17 protons, 20 neutrons
• Ions

  Atoms which have an overall charge due to losing or gaining electrons
• Sodium ion

  • 11 protons, 12 neutrons, 10 electrons (1+ charge)
• Oxide ion

  • 8 protons, 8 neutrons, 10 electrons (2- charge)
• Aluminium ion

  • 13 protons, 14 neutrons, 10 electrons (3+ charge)