Why does silicon have a high melting temperature?

Answer 1

Silicon forms what is known as a network covalent solid. Most covalent compounds that involve a couple atoms bonded together to form a molecule, and those molecules attracted to each other through weak intermolecular forces. Because these forces are relatively weak (compared to covalent or ionic bonds), molecules are easily separated from each other and so covalent compounds typically have low melting points. Silicon atoms are different. They form huge networks of strong covalent bonds with each other, essentially making huge molecules with atoms that are not easy to separate. A great example of another network covalent solid is a diamond (carbon atoms bonded together in a huge network). So if you look at a diamond you are essentially looking at one huge molecule--all the atoms covalently bonded together.