Periodicity

• s, p, d blocks


  Classification of elements according to which orbitals the highest energy electrons are in
• Elements


  • Classified as s, p or d block
  • Highest energy electrons are in different orbitals
• Atomic radius decreases from left to right across a period
• Exactly the same trend in period 2
• Periodicity

  Repeating pattern across different periods
• Properties that display periodicity

  • Atomic radius
  • Melting points
  • Boiling points
  • Ionisation energy
• Elements are arranged in increasing atomic number in the periodic table

  
• Elements in Groups

  Have similar physical and chemical properties
• Elements in periods show repeating trends in physical and chemical properties
• Period 2


  • Li, Be, B, C, N, O, F, Ne
• Period 3


  • Na, Mg, Al, Si, S, Cl, Ar
• First ionisation energy


  Energy needed to remove an electron from each atom in one mole of gaseous atoms
• The equation for 1st ionisation energy always follows the same pattern
• Factors affecting ionisation energy

  • Attraction of the nucleus
  • Distance of electrons from nucleus
  • Shielding of nuclear attraction
• Successive ionisation energies give information about electronic structure
• Big jump between 4th and 5th ionisation energies

  Indicates the 5th electron is in an inner shell closer to the nucleus with less shielding
• Helium has the largest first ionisation energy
• Metallic bonding

  Electrostatic force of attraction between the positive metal ions and the delocalised electrons
• Factors affecting strength of metallic bonding

  • Number of protons/Strength of nuclear attraction
  • Number of delocalised electrons per atom
  • Size of ion
• Macromolecular structure

  Giant molecular structures with many strong covalent bonds
• Macromolecular structures

  • Diamond
  • Graphite
  • Silicon dioxide
• Giant metallic lattice

  Structure of metallic bonding
• Macromolecular and metallic solids are insoluble in water
• Metallic solids are malleable
• Metallic solids are shiny
• Melting and boiling points increase from Na to Mg to Al due to stronger metallic bonding
• Silicon has very high melting and boiling points due to its macromolecular structure with many strong covalent bonds
• Cl2, S8, P4 have low melting and boiling points due to weak intermolecular forces between simple molecules
• Argon has very low melting and boiling points as it is a monoatomic gas with only weak London dispersion forces
• The trend in period 2 is similar, with Li and Be having high melting points due to metallic bonding, B and C having very high melting points due to macromolecular structures, and N2, O2, Ne having low melting points as they are simple molecular or monoatomic gases
• How are elements classified in the periodic table?

  Elements are classified as s, p, or d block based on their highest energy electrons' orbitals.

  
• Why do atomic radii decrease as you move from left to right across a period?

  Atomic radii decrease due to increased positive charge attraction from protons for electrons in the same shell.
• What is the trend in atomic radius in period 2?

  The trend in atomic radius in period 2 is the same as in other periods, decreasing from left to right.
• What is periodicity in the context of the periodic table?

  • Periodicity refers to a repeating pattern across different periods.
  • Properties such as atomic radius, melting points, boiling points, and ionization energy display periodicity.
• How are elements arranged in the periodic table?

  Elements are arranged in increasing atomic number.
• What do elements in the same group have in common?

  Elements in the same group have similar physical and chemical properties.