Detail of non metals?

The elements generally regarded as nonmetals are: * hydrogen (H) * In Group 14: carbon (C) * In Group 15(the pnictogens): nitrogen (N), phosphorus (P) * Several elements in Group 16, the chalcogens: oxygen (O), sulphur (S), selenium (Se) * All elements in Group 17 - the halogens * All elements in Group 18 - the noble gases Common properties considered characteristic of a nonmetal include: * poor conductors of heat and electricity when compared to metals * they form acidic oxides (whereas metals generally form basic oxides) * in solid form, they are dull and brittle, rather than metals which are lustrous, ductile or malleable * usually have lower densities than metals * they have significantly lower melting points and boiling points than metals * non-metals have high electronegativity