Chemical Bonding and Properties: Silicon Carbide, Boron Nitride, and Bronze

Which statements about silicon carbide, boron nitride and bronze are correct?

I. All of these substances are bonded covalently.
II. All of these substances have high melting points.
III. Boron nitride and bronze can conduct electricity in solid state but not pure silicon carbide.

Final Answer:

All of these substances are covalently bonded. They all have high melting points. While boron nitride and bronze can conduct electricity, silicon carbide can't conduct electricity very well.

The statements about silicon carbide, boron nitride, and bronze are as follows:

This statement is correct. Silicon carbide is a covalent compound where each silicon atom bonded to four carbon atoms, and boron nitride also has a similar structure to graphite with covalent bonding. On the other hand, bronze is an alloy of copper and often tin, zinc, or other elements, and is metallically bonded not covalently.

This statement is also correct. Both silicon carbide and boron nitride are covalent compounds that have high melting points due to the strong, three-dimensional network of covalent bonds in their structures. Bronze, being a metal alloy, also has a high melting point.

This statement is partially true. Boron nitride in its graphite-like form and bronze, as a metallic alloy, can conduct electricity. Silicon carbide, however, can't conduct electricity as good as them because the strong network of covalent bonds leaves no free electrons to carry the charge.