Ionic compounds and formula units Transitional Reasoning Practice

Questions

1. 1.

   A chemist examines a solid crystalline ionic compound containing metal cations $M^{3+}$ and non-metal anions $X^{2-}$ arranged in an extended three-dimensional lattice. Structural analysis confirms that the solid consists of a continuous network of alternating ions held by electrostatic attractions rather than isolated groups. Based on the fundamental nature of ionic structures, which statement correctly identifies the formula unit of this compound and the scientific reason for using this term instead of "molecular formula"?

   • A) $M_3X_2$, because it represents the actual number of bonded atoms forming an individual neutral molecule inside the crystal.
   • B) $M_2X_3$, because it represents the simplest whole-number ratio of ions in the continuous lattice rather than a discrete molecular entity.
   • C) $M_2X_3$, because ionic compounds only exist as pairs of discrete molecules that share electrons equally in the solid state.
   • D) $M_6X_9$, because the chemical formula must directly reflect the coordination numbers of the constituent ions in the crystal lattice.

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