Why do nonmetals have a negative melting point?

Question

(In Fahrenheit)

Answer 1

Not all of them do: carbon has one of the highest known melting points (it will actually sublime unless under pressure, but the temperature is still extremely high).  Boron, sulfur, phosphorus, and iodine also have melting points well above room temperature.

The melting and boiling points of substances depend upon the types and strengths of the

The other nonmetals are oxygen, nitrogen, the halogens, and the noble gases.  Noble gases only experience weak dispersion forces between their atoms, so there is little force to overcome the thermal motion of the atoms and pull them into a liquid or solid.  Similarly, halogens, nitrogen, and oxygen form diatomic molecules.  These molecules have perfectly nonpolar bonds between atoms, so again, weak dispersion forces dominate.  Iodine is heavy enough that it is a solid at room temperature, but has a relatively low melting point nonetheless.  In contrast, the high melting point nonmetals mentioned above form large molecules (sulfur, white phosphorus - though S8 and P4 have pretty low melting points compared to the network solids like C (diamond) and B) or crystals with every atom connected to several others by covalent bonds (carbon - diamond and graphite, boron, red and black phosphorus).