Argon, with the atomic number 18, is a chemical element belonging to group 18 of the periodic table and is the third most abundant gas in Earth’s atmosphere. This non-combustible, colourless, and odourless gas has a molecular formula of Ar and a density higher than air. Argon is commonly used in monatomic form in fluorescent tubes.
Argon was the first noble gas identified by scientists. In 1894, Scottish chemist William Ramsay and English physicist Lord Rayleigh discovered argon’s existence. The name "argon" comes from the Greek word "argos," meaning "inactive" or "lazy," reflecting its inert nature.
Argon belongs to the noble gas family and makes up about 0.93% of Earth’s atmosphere, making it the third most abundant gas in our environment. Noble gases like argon are known for being non-flammable, cryogenic, and chemically unreactive.
When heated, argon emits a blue-violet glow. Argon lasers produce a characteristic blue-green light. Due to its complete valence electron shell, argon is chemically inert, typically in the 0 oxidation state.
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(Session 2026 - 27)