3.1.1 - Periodicity

• Electron Configuration


  Arrangement of electrons into orbitals and energy levels around the nucleus of an atom/ion
• First Ionisation Energy

  Removal of one mole of electrons from one mole of gaseous atoms.
• Factors affecting first Ionisation energy

  1. Strength of attraction between the electron and the nucleus
  2. Nuclear charge
  3. Atomic radius
• Giant covalent lattice

  Network of atoms bonded by strong covalent bonds

  • Typically insoluble with high melting and boiling points due to the presence of strong covalent bonds.
  • Poor electrical conductors; no mobile charged particles.
• Giant Metallic Lattice Structure

  The strong electrostatic forces of attraction between the giant proton lattice in a ’sea’ of delocalised electrons

  • Typically insoluble
  • High boiling and melting points
  • Good conductor; Presence of delocalised electrons
• Anisotrophic: Different properties depending on the orientation of the crystal.
• Periodicity

  Repeating trend in physical and chemical properties across the periods of the periodic table.
• Successive Ionisation Energies

  Energy required to removed each electron one-by-one from one mole of gaseous atoms/ions.
• Group 2 compound uses:

  • Ca(OH)2 - neutralise acidic soils in agriculture
  • Mg(OH)2 & CaCO3 - antacids for neutralisation
• Group 2 reactions

  • Cold Water -> Alkaline Solution (Hydroxide + H2)
  • Steam -> Oxide + H2
  • Oxygen -> Metal Oxide
  • Dilute Acids -> Salt + H2
• Group 2 Solubility

  More soluble down the group

  • Electrostatic attraction between metal ion and hydroxide decreases down the group.
• Diatomic Molecules

  Molecules that are made up of 2 atoms
• Disproportionation

  Oxidation and reduction of the same elements
• Metallic Bonding

  Strong electrostatic attraction between cations and delocalised electrons.

  • Giant metallic lattice structure
• Solid giant covalent lattices

  Networks of atoms bonded by strong covalent bonds.
• Explanation of physical properties of giant metallic and covalent lattices

  In terms of

  • Relative strength of forces
  • Relative strength of bonds
  • Mobility of particles involved.
• Elements are arranged by increasing atomic number
• Periods

  Show repeating trends in physical and chemical properties
• Groups

  Have similar chemical properties.
• Metallic bonding

  Strong electrostatic attraction between cations and delocalised electrons
• Solid giant covalent lattices

  Networks of atoms bonded by strong covalent bonds.
• Halogens Reactivity

  Decreases down the group

  • Lower nuclear attraction on outer valence electrons
  • Increased shielding
  • Greater atomic radius.
• Chlorine benefits: kills bacteria in water, used in bleaching paper and textiles
• Chlorine risks: May form toxic chlorine gas from chlorinated hydrocarbons.