Atomic Properties of O
- Atomic Number of O
- 8
- Atomic Mass of O
- 15.9990 u
- Electron Configuration
- [He] 2s2 2p4
- Electronegativity
- 3.44
- Block
- p-block
- Group
- 16
- Period
- 2
A glowing ember brightens when air reaches it, and oxygen explains why. Oxygen does not burn by itself; it supports combustion by reacting with fuel as atoms rearrange into lower-energy products. Increase the oxygen concentration and many fires grow faster and hotter. The same appetite for electrons drives slower changes too, including the oxidation that rusts iron.
Living cells control oxidation far more carefully. In aerobic respiration, oxygen accepts electrons near the end of a chain of reactions that helps cells extract usable energy from food. Breathing supplies the O2, but hemoglobin, enzymes, and membranes manage its journey. An element associated with flames also makes sustained animal activity possible because biology releases chemical energy in measured steps.
Oxygen makes up about 20.8 percent of the atmosphere and is the most abundant element in Earth's crust by mass, mostly bound inside minerals. Industry separates oxygen from liquefied air for steelmaking, welding, medical support, and chemical production. These uses require careful controls because oxygen-enriched materials can ignite more easily.
Higher in the atmosphere, oxygen changes partners. Three oxygen atoms form ozone, O3, which absorbs much of the Sun's harmful ultraviolet radiation. Near the ground, however, ozone is an irritating pollutant. Location transforms the same molecule from shield to hazard.
Oxygen's Sustainer role depends on disciplined reactivity. It can release energy in a cell, race through a fire, remain locked in rock, or intercept ultraviolet light overhead. The chemistry is energetic; the outcome depends on where and how it happens.