Missing plurals

-UM but not -A

Chemical elements: ACTINIUM, ALUMINIUM, AMERICIUM, BARIUM, BERKELIUM, BERYLLIUM, BOHRIUM, CADMIUM, CAESIUM, CALCIUM, CERIUM, CHROMIUM, CURIUM, DUBNIUM, ERBIUM, EUROPIUM, FERMIUM, FRANCIUM, GADOLINIUM, GERMANIUM, HAFNIUM, HASSIUM, HELIUM, HOLMIUM, INDIUM, IRIDIUM, LAWRENCIUM, LUTETIUM, MEITNERIUM, MOLYBDENUM, NEODYMIUM, NEPTUNIUM, NIOBIUM, NOBELIUM, OSMIUM, PLATINUM, PLUTONIUM, POLONIUM, PROMETHIUM, RADIUM, RHENIUM, RHODIUM, RUBIDIUM, RUTHENIUM, SAMARIUM, SCANDIUM, SEABORGIUM, SELENIUM, SODIUM, TANTALUM, TECHNETIUM, TELLURIUM, TERBIUM, THALLIUM, THULIUM, TITANIUM, URANIUM, VANADIUM, YTTERBIUM, YTTRIUM. (Note that some chemical elements do admit plurals, but that's for another article.)

To do

ALARUM, ALLIUM, ALLUVIUM, ALUM, ALYSSUM, ANTEBELLUM, ANTEPARTUM, ANTHURIUM, ARUM, ASYLUM, AVIZANDUM, BDELLIUM, BEGUM, BLUEGUM, BOOJUM, BUBBLEGUM, BUNKUM, CALADIUM, CAPSICUM, CARDAMUM, CEMENTUM, CERASTIUM, CHECKSUM, CHETRUM, CHILLUM, COCKALORUM, COLCHICUM, COLISEUM, COLLUVIUM, COLOSSEUM, COLOSTRUM, COLUMBIUM, CONUNDRUM, CORIUM, CORUNDUM, CUM, CYMBIDIUM, DECORUM, DEDENDUM, DELIRIUM, DELPHINIUM, DENTALIUM, DEUTERIUM, DIAZONIUM, DIDYMIUM, DINKUM, DOMINIUM, DORONICUM, DRUM, DUMDUM, DYSPROSIUM, EARDRUM, ELECTRUM, EPICARDIUM, EPIMEDIUM, EPIMYSIUM, EPIPHYLLUM, ERYNGIUM, EUPHONIUM, FACTOTUM, FALCIPARUM, FRAENULUM, FRAENUM, FREEMIUM, FRENULUM, FRENUM, GALBANUM, GALLIUM, GELSEMIUM, GERANIUM, GEUM, GLUM, GUAIACUM, GUM, GYPSUM, HABENDUM, HAHNIUM, HARMONIUM, HELENIUM, HOKUM, HOODLUM, HUMDRUM, HYPERICUM, IMPERIUM, INDECORUM, INFIMUM, JEJUNUM, JOLIOTIUM, JORUM, KETTLEDRUM, KHOUM, KUMKUM, LABARUM, LABDANUM, LABURNUM, LADANUM, LANTHANUM, LAUDANUM, LIGUSTRUM, LINOLEUM, LOCUM, LOMENTUM, LUTECIUM, LYCOPODIUM, MAGNUM, MECONIUM, MEERSCHAUM, MENTUM, MODICUM, MUSEUM, MYOCARDIUM, MYOMETRIUM, NASTURTIUM, NATATORIUM, NEUM, NGULTRUM, NOSTRUM, OAKUM, ODIUM, OLEUM, OLIBANUM, OPIUM, OPOSSUM, OPPROBRIUM, ORICHALCUM, ORIGANUM, PABLUM, PABULUM, PANJANDRUM, PANTOUM, PASPALUM, PENDULUM, PEPLUM, PERIMYSIUM, PETROLATUM, PETROLEUM, PHORMIUM, PLENUM, PLUM, POLYGONUM, POMATUM, POPADUM, POPPADUM, POSSUM, POTASSIUM, PRACTICUM, PRAESIDIUM, PRECORDIUM, PREMIUM, PRESIDIUM, PROTIUM, PSALTERIUM, PSYLLIUM, PUERPERIUM, PYRETHRUM, QUADRIVIUM, QUORUM, RHIZOBIUM, RUM, RUMDUM, SANCTUM, SARGASSUM, SCHTUM, SCRUM, SCUM, SEBUM, SEDUM, SESAMUM, SHTUM, SKOOKUM, SLUM, SOLANUM, SORGHUM, SPHAGNUM, SPLENIUM, SPUTUM, STELLIUM, STEPMUM, STEWBUM, STICKUM, STRAMONIUM, STRUM, STUM, STUMBLEBUM, SUGARPLUM, SUM, SUPREMUM, SWUM, TALCUM, TAPETUM, TECTUM, TEDIUM, TEETOTUM, THRUM, TRIDUUM, TRILLIUM, TRITIUM, TROPAEOLUM, UROPYGIUM, VALLUM, VARIORUM, VELLUM, VERATRUM, VERBASCUM, VIBURNUM, WAMPUM, YESSUM.