Hafnium rhymes with:
ammonium, capernaum, condominium, cranium, didinium, geranium, gonium, harmonium, millennium, minium, neptunium, pandemonium, plutonium, polonium, selenium, titanium, uranium, zirconium
Hafnium sounds like:
habben, hafeman, hafen, hafnia, hapeman, happen, havana, haveman, havemann, haven, havin', heaven, heavin, hibben, hibma, hipbone, hippen, hoban, hoben, hobin, hoffman, hoffmann, hofman, hofmann, hooven, hopman, hovan, hoven, hovnanian, huffine, huffman, hyphen