A student sketches one layer of an MgO crystal as a 4×4 square grid in which the…
CHEMISTRY · Single correct · AP · Chemistry · Compound Structure and Properties · Compound Structure and Properties
Problem
A student sketches one layer of an MgO crystal as a 4×4 square grid in which the pattern along every row is Mg²⁺, O²⁻, Mg²⁺, O²⁻. In the next layer directly above, the student places Mg²⁺ ions directly over the Mg²⁺ ions in the first layer.
Which statement best explains why this representation is inconsistent with the actual structure of MgO?
(a) Charge neutrality is lost because the upper layer contains only Mg2+ ions, giving the crystal a net positive charge
(b) The sketch ignores that Mg2+ ions are significantly smaller than O2− ions, so the positions shown cannot represent the lowest-energy lattice
(c) Like-charged Mg2+ ions are positioned directly above one another, creating strong electrostatic repulsion that would destabilize the lattice
(d) Ions in an ionic solid have no preferred orientation, so any regular repeating pattern is unrealistic