Periodicity

• Periodicity - repeating patterns across different periods
• What is the trend across periods?

  • same shielding due to same number of shells
  • but there is 1 more proton as you go across the period
  • therefore there is a bigger nuclear charge
  • this attracts the shells inwards
  • which reduces the atomic radius
• Why do atoms get bigger as you go down the group?

  shielding increases due to an increase in electrons

  nuclear charge increases but is outweighed by distance and shielding

  so there is less attraction from nucleus to the outer electron

  therefore the atomic radius increases
• Electronegativity - ability of an atom to attract the shared pair of electrons in a covalent bond