I001 - Ionics

• LQ: explain the term "effective nuclear charge".

  The effective nuclear charge experienced by an atom's outer electrons increases across a period because nuclear charge increases.
• What is an ion?

  An ion is an electrically charged particle that has gained stability, lower enthalpy compared to the separate ions.
• What does isoelectronic mean?

  Same number of electrons but different number of protons.
• How are ionic bonds formed?

  Formed by strong electrostatic attractions between oppositely charged ions.
• LQ - Why is ionic bonding an example of a redox reaction?

  Metal atom loses valence electrons so is oxidised.

  Non-metal atom gains electrons so is reduced.

  This occurs simultaneously, therefore this is a redox reaction
• Geometry of an ionic crystal lattice varies depending on what 3 factors?

  • Ionic charge
  • Ionic radius
  • Relative number of ions
• Solubility of ionic lattices

  Ionic compounds are soluble in polar substances, like water, but insoluble in non-polar substances, like hexane. The partial charges in water molecules form ion-dipole attractions with ions in the ionic lattice. The ions separate from the lattice become surrounded by water molecules, becoming hydrated and hence dissolving
• LQ S3.1 How can lattice enthalpy + bonding continuum explain trend in melting points of metal chlorides across period 3?

  • Ionic and covalent bonding are 2 extremes, many substances show covalent bonds with ionic character
  • Bond polarity calculated from the change in electronegativity values of the 2 atoms
• Why are ionic compounds only soluble when the solvent is polar?

  Ion-dipole forces of attraction are formed between polar solvents and the charged ions of an ionic compound. The energy released by this process is often enough to overcome the energy required to separate the ions in the lattice. Ionic substances are not usually soluble in non-polar solvents, as the forces of attraction between an ion and a non-polar molecule (London forces) are much weaker than ion-dipole forces, so the electrostatic forces of attraction between the oppositely charged ions in the lattice are not overcome.