In electrides, the anions (negative ions) are
completely replaced by electrons, which are trapped in
naturally formed cavities within a framework of regularly
stacked cations (positive ions). Unlike other types of
anions, anionic electrons do not behave as if they were
simple charged spheres. The properties of an electride
depend largely on the distance between the cavities that
hold trapped electrons. When the trapped electrons are far
apart, they do not interact strongly, and so behave
somewhat like an array of isolated negative charges.
When they are closer together, they begin to display
properties associated with large ensembles of identical
particles. When they are still closer, the ensemble
properties dominate and the electrons “delocalize”.
- It can be inferred from the passage that an electride
behaves most like a normal ionic crystal when the
electride has which of the following features?
(A) The anionic cavities are widely separated.
(B) All of the trapped electrons are able to delocalize.
© The trapped electrons are liberated by
impinging photons.
(D) The ions are tightly packed together.
(E) Most of the cations have lost their electrical
charge.
The correct answer is A. But I couldn’t find any clue about “normal ionic crystal”. Please help me, thanks！