LATTICE ENTHALPIES

• FACTORS AFFECTING LATTICE ENTHALPY?

  • ion size
  • charge
• HOW DOES CHARGE AFFECT LATTICE ENTHALPY?

  greater charge = larger enthalpy
• HOW DOES ION SIZE AFFECT LATTICE ENTHALPY?

  larger ions = smaller enthalpy
• WHAT DOES DISCREPANCY BETWEEN EXPERIMENTAL AND THEORETICAL VALUES SUGGEST (ZnSe EXAMPLE)?

  • extra bonding present
  • Zn(2+) relatively small with high positive charge
  • Se(2-) relatively large with high positive charge
  • Zn(2+) can distort electron clouds of Se(2-) as Se(2-) is large with electrons far from the nucleus
  • causing more electrons between nuclei than expected
  • Se(2-) is polarised