Sapphire is the common name for the blue variety of the mineral corundum. Corundum is a crystal form of aluminum oxide (Al2O3). A model of the extended structure of corundum is shown below.

Question

Which statement describes the extended structure of corundum?
A.
subunits of aluminum oxide that are arranged in no particular pattern
B.
layers of aluminum and oxygen that are arranged in no particular pattern
C.
layers of only oxygen that are arranged next to layers of only aluminum
D.
subunits of aluminum oxide that are arranged into a repeating pattern

Answer 1

The correct answer is:

D. subunits of aluminum oxide that are arranged into a repeating pattern

Corundum has a crystalline structure, which means that its constituent particles (in this case, aluminum and oxygen) are arranged in a regular, repeating pattern throughout the crystal lattice.