Words That Rhyme With "Promethium" :

3 syllables:

lithium

4 syllables:

androecium, cyathium, gynoecium, lutecium, lutetium, podetium, technetium

5 syllables:

amphithecium, apothecium, cleistothecium, endothecium, epithecium, hypothecium, nemathecium, perithecium