atomic number 18

Từ điển WordNet v3.1 - WordNet Dictionary

noun

a colorless and odorless inert gas;
one of the six inert gases;
comprises approximately 1% of the earth's atmosphere
• Syn:
argon, Ar
• Hypernyms:
chemical element, element, noble gas, inert gas, argonon
• Substance Holonyms:
air