In the paper ‘Predicted chemical bonds between rare gases and Au’ (J. Am. Chem. Soc., 1995, 117, 2067), P. Pyykkii used a computational study of the species RgAuRg⁺ and AuRg⁺ (where Rg refers to a ‘rare’ gas) to predict the bond energies and bond lengths of the Au–Rg bond. Why did the author draw parallels between the Au–Rg bonds and H–Rg bonds? Give the values of bond energy and bond length for the series of Au–Rg bonds. How would these values be expected to differ for Cu–Rg⁺ species? List the values of the analogous Cu–Rg⁺ bonds and rationalize the differences.