Periodicity

• How is the periodic table arranged?

  By atomic number.
• What is the periodic trend in metals?

  Melting points increase across the period
• Explain the periodic trend in metals

  The metal metal bonds get stronger

  Because the metal ions have an increasing number of delocalised electrons

  And a decreasing ionic radius

  Which leads to a higher charge density, attracting ions together more strongly
• Describe the periodicity trend of giant covalent structures(C,Si)

  Highest melting points in their period
• Explain the periodicity trend of giant covalent structures(C,Si)

  Strong covalent bonds

  Lots of energy needed to break the bonds
• Describe the periodicity trend of simple molecular structures

  Low melting points
• Explain the periodicity trend of simple molecular structures

  Intermolecular forces are weak so need little energy to break the bonds
• State and explain the period trends in noble gasses

  Lowest melting point

  Exist as monotonic resulting in very weak intermolecular forces
• Factors effecting ionisation enthalpies

  Atomic radius - Further the outer shell is from the positive nucleus less they will be attracted to it (Lower)

  Nuclear charge - Positive charge from nucleus caused by protons. More protons more attraction (Higher)

  Electron shielding - Inner electrons shield outer shell electrons from attractive force of nucleus, more shells more shielding (Lower)
• First ionisation enthalpies decrease down a group
• Why do first ionisation enthalpies decrease down a group?

  The outer electrons are further away from the nucleus, so less attracted

  Amount of shielding increases meaning less nuclear attraction
• Fist ionisation enthalpies increase across a period
• Why do first ionisation enthalpies increase across a period?

  The number of protons is increasing, so the outer electrons are attracted more strongly to the nucleus
• Where are there small drops in first ionisation enthalpies across the Groups?

  Group 2 and 3

  Groups 5 and 6
• S block metals have low ionisation enthalpies
• Why do S block metals have low ionisation enthalpies?


  They have relatively low nuclear charges