Periodicity

• how are the elements arranged in the periodic table?

  in order of increasing atomic number
• what is meant by periodicity?

  the repeating trends in chemical and physical properties
• define first ionisation energy


  the energy required to remove one electron from each atom in one mole of a gaseous element to for one mole of gaseous +1 ions
• factors that effect ionisation energy

  • atomic radius
  • nuclear charge
  • electron sheilding
• first ionisation energy increases across period 3 because of

  • increased nuclear charge
  • decreased atomic radius
  • same electron shielding