S block

• First IE is low for all elements - metals are very reactive

  • increase in atomic radii down the group means IE decreases
• Diagonal relationship

  • 'head' element of the group displays different behaviour to the rest of the group
  • smaller radii - high charge density
  • bonding shows a high degree of covalent character
  • the head elements share characteristics with the element diagonally bottom right to it
• Hard Lewis acid: can donate a pair of electrons to a lone pair of electrons

  • very polarising
• Soft Lewis acids are weak acids that can donate a proton to a lone pair of electrons

  • easily deformed electron clouds
• Group 1 are strong reducing agents

  • easily oxidised (only 1 valence electron)
  • large atomic radii
• Li is the only alkali metal to form an nitride from exposure to N2 at RTP (Li3N has a high lattice energy)Alkali metal-azides can be synthesised

  • metal amine + nitrous oxide (N2O)

  
• S-block metal hydrides react readily with water
• All group 1 halides are soluble in water except LiF (high lattice enthalpy)
• Group 1 oxides are prepared by heating with limited O2 or by thermal decomposition of the super/peroxides

  • Oxide (O 2-)
  • Peroxide (O2 2-)
  • Superoxide (O2 1-)
  • all are basic upon reaction with water
  • Super + peroxides stability increases down the group - based on lattice enthalpy
• Kapustinskii's equation

  • calculates the lattice enthalpy for an ionic crystal
  • V = no. ions in the formula of the compound
  • Use picometers for ionic radii

  
• Group 1 metals can be burned in ozone - onzonides (MO3)

  • unstable + explode violently
  • 'bent' shape
• Cryptans are bicyclic 3D versions of crown ethers

  • the metal is completely surrounded
  • very selective on which metal cation it surrounds
• Be and Mg have no flame test colour

  • smaller radii + high Zeff
  • a larger amount of energy is required for excitation
• Group 2 metallic bonding is stronger than group 1 elements

  • 2 valence electrons
  • higher melting points
  • are physically harder
• Thermal stabilises of peroxides increases down the groups
• Group 2 nitrides (M3N2)

  • formed from heating in N2
  • react with water to form ammonia
• Quasilinear - when the calculated energy difference between linear and bent shapes (with a change of >20°) is less than 4 kJ mol-1
• Inverse polarisation occurs when the metal ion is polarised by a halogen

  Bending increases with increasing polarisability of the metal ion

  Larger elements in the group can only have good orbital overlap when the molecule is bent

  
• Metallocenes

  • group 2 metals can coordinate to 2 cp ligands
  • Be has a slipped-sandwiched structure - one is bound normally and the other is bound through a pz orbtial on a C (𝛈1)
  • Mg is a linear sandwich structure - mostly ionic bonded
  • sensitive to water + air
  • heavier metals adopt a bent sandwich structure