Which property is shared by Diamond, Graphite, and Silicon Dioxide?

• A. They have high melting or boiling points due to strong covalent bonds
• B. They are soluble in water
• C. They form simple molecular lattices
• D. They conduct electricity equally

Answer: (A)

All three substances share a giant covalent network structure, where atoms are linked by strong covalent bonds in a continuous 3D lattice. Breaking such a structure apart requires disrupting many bonds, which needs a lot of energy, so their melting or boiling points are very high. In diamond, every carbon forms four strong bonds in a rigid tetrahedral lattice, making it extremely resistant to heat. In graphite, carbon atoms are bonded tightly within layers, giving high in‑layer bond strength, though the layers themselves are held together by weaker forces; the result is still a very high energy requirement to change state. In silicon dioxide, silicon and oxygen form a vast network of strong Si–O bonds throughout the solid, so it also has a very high melting point.