CHEMISTRY · Single correct · A Level · Chemistry · Bonding · Bonding
Problem
Calcium carbonate, CaCO₃(s), contains CO₃²⁻ ions that are planar triangular. Which statement about the orientation of CO₃²⁻ ions relative to Ca²⁺ ions in the crystal is most consistent with minimizing electrostatic repulsion?
(a) Each Ca²⁺ ion lies directly on top of one O atom in a CO₃²⁻ ion, maximizing overlap of positive and negative charge.
(b) Each Ca²⁺ ion is situated in the plane of a CO₃²⁻ ion, halfway between two O atoms, so the cation is closest to two O atoms and farther from the third.
(c) Each Ca²⁺ ion is positioned above the center of a CO₃²⁻ plane so that the cation is equidistant from all three O atoms.
(d) Each Ca²⁺ ion is located along the axis passing through the carbon atom on the side opposite the O atoms, keeping the cation near the central atom rather than the oxygens.