Atomic Structure & the Periodic Table

• Particle: Proton

  Relative Charge: +1

  Mass (atomic mass): 1
• Particle: Neutron

  Relative Charge: 0

  Mass (atomic mass): 1
• Particle: Electron

  Relative Charge: -1

  Mass (atomic mass): 1 / 1837
• Proton number: number of protons in an atom (and number of electrons in an atom)
• Nucleon number: number of protons + neutrons in an atom
• In the periodic table

  • The proton number increases by 1 when you go to the right
  • When you go one element down, you increase proton number by 8 in the first 3 periods (transition elements not included)
• Isotopes: atoms of the same elements which have the same protons number, but different nucleon number E.g. Carbon 12 and Carbon 14.
• Two types of Isotopes:

  • non-radioactive isotopes
  • radioactive isotopes which are unstable atoms that break down giving radiations
• Medical use of isotopes: cancer treatment (radiotherapy) – rays kill cancer cells using cobalt-60
• Industrial use of Isotopes: to check for leaks – radioisotopes (tracers) added to oil/gas. At leaks radiation is detected using a Geiger counter.
• Electrons are arranged in electron shells.
• Atoms want to have full outer shells (full set of valency electrons), this is why they react.
• Noble gases have full outer shells so they have no need to react.
• Electron shell structure: 2, 8, 8, 18.
• More reactive elements have a greater desire to have a full outer shell, so also form more stable compounds.