atomic number 69

Từ điển WordNet v3.1 - WordNet Dictionary

noun

a soft silvery metallic element of the rare earth group;
isotope 170 emits X-rays and is used in small portable X-ray machines;
it occurs in monazite and apatite and xenotime
• Syn:
thulium, Tm
• Hypernyms:
metallic element, metal
• Substance Holonyms:
apatite, monazite, xenotime