The image below is part of a computer-generated model representing covalently bonded nonmetal atoms arranged in a crystal lattice. Four small atoms are bonded to each large atom. The structure extends in every direction. The covalent network solid represented by the model likely
A.
is hard and strong.
B.
has a low melting point.
C.
is an electrical conductor when in the molten state.
D.
is a good conductor of both heat and electricity.

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.

Hope this helped :)