The lattice energy of an ionic compound increases when

Correct answer: A. the charges on the ions increase and their radii decrease

  • A. the charges on the ions increase and their radii decrease
  • B. the charges on the ions decrease
  • C. the ions become larger
  • D. the compound is dissolved in water

Explanation

Electrostatic attraction is proportional to the product of the charges and inversely proportional to the distance between the ion centres, so small, highly charged ions pack closely and bind strongly. This is why magnesium oxide, with 2+ and 2- ions, has a far higher lattice energy and melting point than sodium chloride. Dissolving the compound breaks the lattice rather than strengthening it.

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About Lattice Energy

Lattice energy describes the energy released when gaseous ions form one mole of an ionic solid, or the energy required to separate that solid into gaseous ions, depending on the convention used. Its value depends mainly on ionic charge and radius and is calculated through Born-Haber cycles.

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