Monatomic elements

Group 0 elements (the noble gases) including Helium, Neon and Argon, exist as single, unattached particles. They are stable atoms. They have fuller outer energy levels so they do not usually form molecules with other atoms.

An abridged periodic table highlighting helium, neon and argon.

They have low melting and boiling points as they are easily separated by overcoming the weak forces of attraction between the atoms.

Summary of bonding

StructureDensityMelting PointConduction
Monatomic (noble gas)LowLowNon-conductor
Covalent molecular (N2, P4, S8)LowLowNon-conductor
Covalent networkVery highVery highNon-conductor (except graphite)
Metallic lattice (all metals)HighHighConductor