Ionic solids (NaCl, CaO, etc.) typically have

Answer: High melting points and brittle behavior Strong electrostatic attractions between cations and anions → high BP/MP. Brittle because shifting layers brings like charges together → repulsion → fracture.

Lattice energy of an ionic compound increases with

Answer: Smaller ionic radii and larger ionic charges Coulomb's law: U ∝ q₁q₂/r. Smaller r and larger |q| → stronger attraction → larger (more negative) lattice energy.

Why does Al2O3 have the largest lattice energy?

Answer: Larger ionic charges (3+ and 2-) increase the electrostatic attraction Lattice energy is proportional to (q1·q2)/r; the larger product of charges in Al2O3 dominates and makes its lattice energy by far the largest.

AP Chemistry · Topic 2.3

Structure of Ionic Solids Practice

Part of Compound Structure and Properties.(SAP-3.C)

Practice questions

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Sample questions

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Sample 1difficulty 2/5
$Ionic solids (NaCl, CaO, etc.) typically have$
- A
  $Metallic conductivity in solid form$
- B
  $No charged species$
- C
  $High melting points and brittle behavior$
  check_circle
- D
  $Low melting points$
Why
$Strong electrostatic attractions between cations and anions → high BP/MP. Brittle because shifting layers brings like charges together → repulsion → fracture.$
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Sample 2difficulty 3/5
$Lattice energy of an ionic compound increases with$
- A
  $Larger radii$
- B
  $Decreasing charges$
- C
  $Random$
- D
  $Smaller ionic radii and larger ionic charges$
  check_circle
Why
$Coulomb's law: U \propto q₁q₂/r. Smaller r and larger |q| \to stronger attraction \to larger (more negative) lattice energy.$
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Sample 3difficulty 3/5
$The bar chart compares lattice energies of four ionic compounds. Lattice energy magnitude depends on ion charges and the distance between them.$
$Why does Al2O3 have the largest lattice energy?$
- A
  $Al has lower ionization energy than Na$
- B
  $Smaller atoms automatically yield higher lattice energies$
- C
  $Larger ionic charges (3+ and 2-) increase the electrostatic attraction$
  check_circle
- D
  $It contains more atoms per formula unit$
Why
$Lattice energy is proportional to (q1\cdotq2)/r; the larger product of charges in Al2O3 dominates and makes its lattice energy by far the largest.$
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Sample 4difficulty 4/5
$Which compound has the largest (most exothermic) lattice energy?$
- A
  $MgO$
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- B
  $CaF_2$
- C
  $NaCl$
- D
  $KBr$
Why
$\propto |q_+ q_-|/r$
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Sample 5difficulty 4/5
$Lattice energies for the alkali fluorides decrease in the order LiF > NaF > KF.$
$The trend is best explained by:$
- A
  $Differences in covalent character$
- B
  $Increasing cation size means greater cation-anion separation, weakening Coulombic attraction$
  check_circle
- C
  $Increasing nuclear charge of the cation$
- D
  $Increasing F- charge$
Why
$All compounds have ions with the same charges; only the cation radius changes (Li < Na < K), which increases r and weakens lattice energy.$
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