Monatomic rhymes with:
atomic, diatomic, subatomic, atomic, diatomic, subatomic, tomich, adamec, adamik, atomic, autonomic, comic, diatomic, economic, ergonomic, gastronomic, islamic, macroeconomic, microeconomic, noneconomic, romick, socioeconomic, subatomic, technomic, tomich, tragicomic, uneconomic
Monatomic sounds like:
maddening, madding, madness, madonna's, maidens, maintaining, maintains, maintenance, mandamus, mandating, manhattan's, matinees, mating, matting, meat-eating, medianews, mediating, meditating, meditations, mediums, mednick, meeting, meeting's, meetings, mending, mendonca, mendonsa, mentink, mentioning, mentions, methanex, mindedness, minding, minnetonka, minting, mitnick, mittens, modems, monadnock, monotonous, montana's, montanans, montanez, motioning, motions, motown's, mountain's, mountainous, mountains, mounting, mouthing, muddying, munitions, mutating, mutations, muting, mutinies, mutinous