Discovery date : 1894
Discovered by: Lord Rayleigh and Sir William Ramsay
Origin of the name: The name is derived from the Greek, 'argos', meaning idle.
Allotropes : -
~>ARGON is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in the atmosphere of Earth.
| FACT BOX | |||
| Group | 18 | Melting point | −189.34°C, −308.81°F, 83.81 K |
| Period | 3 | Boiling point | −185.848°C, −302.526°F, 87.302 K |
| Block | p | Density (g cm−3) | 0.001633 |
| Atomic number | 18 | Relative atomic mass | 39.948 |
| State at 20°C | Gas | Key isotopes | 40 Ar |
| Electron configuration | [Ne] 3s23p6 | CAS number | 7440-37-1 |
| ChemSpider ID | 22407 | ChemSpider is a free chemical structure database | |
Although argon is abundant in the Earth’s atmosphere, it evaded discovery until 1894 when Lord Rayleigh and William Ramsay first separated it from liquid air. In fact the gas had been isolated in 1785 by Henry Cavendish who had noted that about 1% of air would not react even under the most extreme conditions. That 1% was argon.
Argon was discovered as a result of trying to explain why the density of nitrogen extracted from air differed from that obtained by the decomposition of ammonia.
Ramsay removed all the nitrogen from the gas he had extracted from air, and did this by reacting it with hot magnesium, forming the solid magnesium nitride. He was then left with a gas that would not react and when he examined its spectrum he saw new groups of red and green lines, confirming that it was a new element.