A previous approach (Hancock, R. D.; Bartolotti, L. J. Inorg. Chem. 2005, 44, 7175) using DFT calculations to predict log K-1 (formation constant) values for complexes of NH3 in aqueous solution was used to examine the solution chemistry of Rg(I) (element 111), which is a congener of Cu(I), Ag(I), and Au(I) in Group 1B. Rg(I) has as its most stable presently known isotope a t(1/2) of 3.6 s, so that its solution chemistry is not easily accessible. LFER (Linear free energy relationships) were established between Delta E(g) calculated by DFT for the formation of monoammine complexes from the aquo ions in the gas phase, and Delta G(aq) for the formation of the corresponding complexes in aqueous solution. For M2+, M3+, and M4+ ions, the gas-phase reaction was [M(H2O)(6)](n+)(g) + NH3(g) = [M(H2O)(5)NH3](n+)(g) + H2O(g) (1), while for M+ ions, the reaction was [M(H2O)(2)](+)(g) + NH3(g) = [M(H2O)NH3](+)(g) + H2O(g) (2). A value for Delta G(aq) and for Delta E for the formation of M = Cu2+ in reaction 1, not obtained previously, was calculated by DFT and shown to correlate well with the LFER obtained previously for other M2+ ions, supporting the LFER approach used here. The simpler use of Delta E values instead of Delta G(aq) values calculated by DFT for formation of monoamine complexes in the gas phase leads to LFER as good as the Delta G-based correlations. Values of Delta E were calculated by DFT to construct LFER with M+ = H+, and the Group 1B metal ions Cu+, Ag+, Au+, and Rg(+), and with L = NH3, H2S, and PH3 in reaction 3: [M(H2O)(2)](+)(g) + L(g) = [M(H2O)L](+)(g) + H2O(g) (3). Correlations involving Delta E calculated by DMol3 for H+, Cu+, Ag+, and Au+ could reliably be used to construct LFER and estimate unknown log K-1 values for Rg(I) complexes of NH3, PH3, and H2S calculated using the ADF (amsterdam density Functional) code. Log K-1 values for Rg(I) complexes are predicted that suggest the Rg(I) ion to be a very strong Lewis acid that is extremely 'soft' in the Pearson hard and soft acids and bases sense.