Answer:
A: is hard and strong
Explanation:
The crystal lattice shown is that of silica, SiO2. For a single molecule of silica to form, the silicon atom would have to form double bonds with each oxygen. Instead, each atom of silicon forms a bond to four different oxygen atoms, each of which is bonded to another silicon atom. This forms a covalent network.
Covalent network solids have the following properties:
They are hard and strong.
They have high melting points.
They usually do not conduct heat.
Silicon dioxide is an electrical semi-conductor.
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