Ionic compounds and formula units Transitional Reasoning Download PDF

Questions

1. 1.

   An analytical chemist determines that a crystalline mineral consists exclusively of calcium cations ($\text{Ca}^{2+}$) and fluoride anions ($\text{F}^-$) arranged in an alternating three-dimensional array held together by electrostatic forces. The analysis confirms that no individual, isolated neutral particles exist within the rigid solid structure. Based on principles of ionic bonding, how should the chemical formula of this mineral be classified and interpreted?

   • A) It is written as $\text{CaF}_2$, representing a formula unit that reflects the simplest whole-number ratio of ions providing overall electrical neutrality, rather than a discrete molecule.
   • B) It is written as $\text{CaF}_2$, representing an isolated molecule consisting of one calcium atom covalently bonded to two fluorine atoms in the solid phase.
   • C) It must be written with coefficients indicating the total count of all ions in the entire macroscopic sample, because ionic lattices lack fixed stoichiometric proportions.
   • D) It is written as $\text{Ca}_2\text{F}$, representing the empirical formula derived from balancing the equal sharing of valence electrons between the metal and non-metal atoms.