The chemical element (symbol Ar) with an atomic number of 18. The third most abundant gas in the Earth's atmosphere, it is a colourless, odourless, inert noble gas.

plural of argon

containing argon.

(physics) A rare stable isotope of argon, ³⁸₁₈Ar, having eighteen protons and twenty neutrons; it amounts to about 0.06% of the element in nature

(physics) The major stable isotope of argon, ⁴⁰₁₈Ar, having eighteen protons and twenty-two neutrons; it amounts to about 99.6% of the element in nature

(physics) A rare stable isotope of argon, ³⁶₁₈Ar, having eighteen protons and eighteen neutrons; it amounts to about 0.3% of the element in nature

(inorganic chemistry) The unstable compound, HArF, formed by reacting argon with hydrogen fluoride

Alternative form of metargon

(geology) A method of estimating the age of igneous rocks or of archaeological objects by measuring the amount of argon that has built up through the radioactive decay of potassium.

plural of potassium-argon dating