Ionic bonds Transitional Reasoning Download PDF

Questions

1. 1.

   A student analyzes the electrostatic attraction in crystalline sodium fluoride (NaF) and magnesium oxide (MgO), noting that both compounds have similar internuclear separation distances between their constituent ions. Despite these similar interionic separations, the melting point of magnesium oxide (2852 °C) is substantially higher than that of sodium fluoride (993 °C). Based on Coulomb's law and the principles of ionic bonding, which statement best explains this significant difference in melting temperatures?

   • A) The electrostatic force of attraction is directly proportional to the product of ionic charges, making the attraction between Mg²⁺ and O²⁻ approximately four times stronger than that between Na⁺ and F⁻.
   • B) Magnesium oxide forms covalent network bonds because the valence electrons are equally shared between magnesium and oxygen atoms.
   • C) Sodium fluoride forms discrete diatomic molecules held by weak intermolecular forces, whereas magnesium oxide forms a three-dimensional lattice.
   • D) The higher melting point of magnesium oxide is caused by the greater atomic mass of magnesium, which prevents thermal vibrations in the lattice.