With the exception of helium, all noble gases solidify at low temperature. The lack of ionic or covalent bonding means that atoms are held together by dispersion forces alone. Given the melting points of the noble gases; Ne = 24 K, Ar = 84 K, Kr = 116 K, Xe = 161 K, what can you say about the strength of the London dispersion forces as the principal quantum number of the outermost shell increases? What is the explanation for this trend?