Nb2AlC and Nb2CTx contain one Nb site and one C site; these are necessarily 'external'. Both MAX phases contain a single Al environment with trigonal prismatic coordination to six niobium atoms. Note that the MXene coordination in Table is described in the absence of termination groups (T). NMR spectroscopy and demonstrated the proximity of 1 H nuclei to the MXene surfaces by using 1 H→ 13 C cross polarization (CP). Hope et al. later quantified the concentrations of -OH and -F terminations on Ti3C2 MXene, which were found to be highly dependent on the synthesis method, and showed the terminations to be intimately mixed using 1 H- F NMR correlation experiments. These observations have been extended to further Ti3C2Tx syntheses and preparation conditions in a pair of very recent reports. In this work, a comprehensive multinuclear NMR study ( 93 Nb, Al, C, 1 H, and 19 F) of the bulk structures and surface chemistry of the known Nbn+1AlCn MAX and Nbn+1CnTx