Ar
Argon is the most abundant noble gas in Earth's atmosphere, comprising nearly 1% of the air.
Physical Properties
| Atomic Mass | 39.948 u |
| Density | 0.0017837 g/cm³ |
| Melting Point | 83.8 K |
| Boiling Point | 87.3 K |
| Appearance | Colorless gas |
| State at Room Temp | Gas |
Chemical Properties
| 1st Ionization Energy | 1520.6 kJ/mol |
| Electron Affinity | -96.0 kJ/mol |
| Oxidation States | 0 |
Atomic Properties
| Electron Configuration | [Ne] 3s2 3p6 |
| Atomic Radius | 71.0 pm |
| Covalent Radius | 106.0 pm |
| Van der Waals Radius | 188.0 pm |
Discovery
| Discovered By | Lord Rayleigh, William Ramsay |
| Discovery Year | 1894 |
| Location | London, England |
| Named After | Greek 'argon' meaning lazy or inactive |
About Argon
Argon is a colorless, odorless noble gas making up 0.934% of Earth's atmosphere. It is produced primarily by radioactive decay of potassium-40. Argon is completely inert under normal conditions and was the first noble gas to be discovered.
Uses & Applications
Welding shielding gas, incandescent and fluorescent lighting, insulating gas in windows, and preservation of historic documents.
Fun Fact
Argon got its name from the Greek word for 'lazy' because it participates in virtually no chemical reactions.
Isotopes
| Mass Number | Abundance | Half-Life | Stable |
| 36 | 0.003336% | - | Yes |
| 38 | 0.000629% | - | Yes |
| 40 | 0.996035% | - | Yes |
Electron Configuration
[Ne] 3s2 3p6