chapter 7 - periodicity

• the first ionisation energy is the energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
• factors affecting ionisation energy

  • atomic radius
  • nuclear charge
  • electron shielding
• increasing the atomic radius decreases the ionisation energy
• increasing the nuclear charge, increases the ionisation energy
• increasing the electron shielding decreases the ionisation energy
• the second ionisation energy is the energy required to remove one electron from each atom in one mole of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions
• ionisation energies increases across each period

  and decrease down a group
• trend in first ionisation energy down a group

  • atomic radius decreases
  • more inner shells so shielding increases
  • nuclear attraction on outer electrons decreases
  • first ionisation energy decreases
• trend in first ionisation energy across a period

  • nuclear charge increases
  • same shell: similar shielding
  • nuclear attraction increases
  • atomic radius decreases
  • first ionisation energy increases
• first ionisation energy across period 2

  • fall from beryllium to boron - marks the start of filling the 2p sub shell
  • fall from nitrogen to oxygen - marks the start of electron pairing in 2p
• metallic bonding is the strong electrostatic attraction between cations and delocalised electrons
• metallic bonding and structure

  • cations are fixed, but electrons are mobile so can carry charge
  • giant metallic lattice
  • strong bonds
  • high melting and boiling points
• metals have high melting and boiling points because they have strong forces of attraction between the delocalised electrons and the cations
• metals are not soluble
• examples of giant covalent structures

  • carbon
  • silicon
• giant covalent structures properties

  • high melting and boiling points because the bonds are strong
  • insoluble in most solvents
  • do not conduct electricity - exceptions = graphene and graphite, as they have 1 free electron per carbon atom which can carry charge
• period 2 melting points

  • increase from Lithium to Carbon (giant structures)
  • decrease from carbon (simple molecules)
• period 3 melting points

  • increase from sodium to silicon (giant structures)
  • decrease from silicon ( simple molecules)