We have computed the methyl cation affinities in the gas phase of archetypal anionic and neutral bases across the periodic table using ZORA-relativistic density functional theory (DFT) at BP86/QZ4P/BP86/TZ2P. The main purpose of this work is to provide the methyl cation affinities (and corresponding entropies) at 298 K of all anionic (XHn-1-) and neutral bases (XHn) constituted by maingroup-element hydrides of groups 14-17 and the noble gases (i.e., group 18) along the periods 2-6. The cation affinity of the bases decreases from H+ to CH3+. To understand this trend, we have carried out quantitative bond energy decomposition analyses (EDA). Quantitative correlations are established between the MCA and PA values.