A model of CaF₂(s) is missing one F⁻ ion that should lie between two adjacent Ca²⁺ ions
PHYSICS · Single correct · ISC · Chemistry · Physics · Chemical Bonding and Molecular Structure
Problem
A model of CaF₂(s) is missing one F⁻ ion that should lie between two adjacent Ca²⁺ ions, causing the two Ca²⁺ ions to become nearest neighbors.
Which of the following revisions would most directly correct the electrostatic inconsistency in the model?
(a) Replace both Ca2+ ions with Mg2+ ions because their smaller size increases lattice energy
(b) Add an extra Ca2+ ion on the opposite side of the unit cell to maintain overall charge neutrality
(c) Insert an F− ion midway between the two Ca2+ ions to restore the alternating charge pattern
(d) Double all Ca2+--F− and F−--F− distances so that repulsive forces are halved everywhere