Oxygen
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Oxygen is the third most abundant element in the universe by mass and is essential to life on Earth.
| Oxygen | |
|---|---|
| Properties | |
| Atomic symbol | O |
| Atomic number | 8 |
| Classification | Non-metal |
| Atomic mass | 15.994 amu |
| Other Information | |
| Date of discovery | 1774 |
| Name of discoverer | Joseph Priestley |
| Name origin | From the Greek words oxus (acid) and gennan (generate) |
| Uses | Supports life |
| Obtained from | From liquid air |
Chemical Properties
At normal atmospheric pressure oxygen melts at 54.36 Kelvin (K) and boils at 90.2 K; on Earth it essentially exists only as a gas. It readily dissolves in water, which makes aquatic life possible. Under normal conditions oxygen forms molecules consisting of two oxygen atoms each sharing two electrons in the 2p subshell; this form of oxygen is known as O2. O2 is a pale blue odourless gas.