What does "atomic number 18" mean?

a colorless and odorless inert gas; one of the six inert gases; comprises approximately 1% of the earth's atmosphere

What is a synonym for "atomic number 18"?

Common synonyms include: ar, argon.

Rare ·Advanced level

Noun

1
a colorless and odorless inert gas; one of the six inert gases; comprises approximately 1% of the earth's atmosphere wordnet