Oxygen Element Properties
Complete reference for Oxygen (O, element 8): atomic data, electron configuration with interactive shell diagram, isotopes, physical constants, and a temperature unit toggle.
Use the Oxygen Element Properties
Oxygen
Nonmetal — Period 2, Group 16
Atomic Identity
Electron Configuration
Two unpaired electrons — triplet ground state (³P₂)
Physical Properties
Isotopes of Oxygen
| Isotope | Symbol | Protons | Neutrons | Mass (u) | Natural Abundance | Stability |
|---|---|---|---|---|---|---|
| Oxygen-15 | ¹⁵O | 8 | 7 | 15.00307 | Radioactive |
Unstable
β⁺ decay, t½ = 122.24 s |
| Oxygen-16 | ¹⁶O | 8 | 8 | 15.99491 | 99.757% | Stable |
| Oxygen-17 | ¹⁷O | 8 | 9 | 16.99913 | 0.038% | Stable |
| Oxygen-18 | ¹⁸O | 8 | 10 | 17.99916 | 0.205% | Stable |
| Oxygen-19 | ¹⁹O | 8 | 11 | 19.00358 | Radioactive |
Unstable
β⁻ decay, t½ = 26.91 s |
Oxygen-16 (¹⁶O) is a doubly magic nucleus (8 protons and 8 neutrons fill complete nuclear shells), making it exceptionally stable. Oxygen-18 (¹⁸O) is used in paleoclimatology — the ¹⁸O/¹⁶O ratio in ice cores and foraminifera shells reveals past ocean temperatures and ice volumes.
Chemical Properties
Atomic Properties
Key Facts About Oxygen
Atmospheric Abundance
Molecular oxygen (O₂) constitutes approximately 20.95% of Earth's dry atmosphere by volume. Nearly all of this oxygen is of biogenic origin — produced by photosynthesis over approximately 2.4 billion years. The Great Oxidation Event (~2.4 Ga) fundamentally transformed Earth's surface chemistry.
Essential for Aerobic Life
Oxygen serves as the terminal electron acceptor in aerobic cellular respiration. Mitochondria use O₂ to oxidize glucose, producing ATP, CO₂, and water. Approximately 90% of the energy used by aerobic organisms comes from O₂-dependent metabolism. It is also a structural component of water (H₂O), making up nearly 89% of water by mass.
Ozone Layer (O₃)
In the stratosphere (15–35 km altitude), oxygen forms ozone (O₃) that absorbs 97–99% of the Sun's harmful ultraviolet radiation (UV-B and UV-C). Without this shield, most surface life would be destroyed by UV damage to DNA. Chlorofluorocarbons (CFCs) catalytically destroy ozone, leading to the Montreal Protocol (1987).
Steel & Industrial Production
The basic oxygen furnace (BOF) uses pure O₂ blown into molten iron to remove carbon and impurities, producing steel. This process accounts for about 70% of global steel production. LOX (liquid oxygen) is also used in rocket propulsion as a powerful oxidizer paired with liquid hydrogen or RP-1 kerosene in engines like SpaceX's Merlin.
Most Abundant Element in Crust
Oxygen is the most abundant element by mass in Earth's crust (approximately 46%), in the hydrosphere (~89% by mass as water), and in the human body (~65% by mass). As silicates and oxides, oxygen bonds dominate rock-forming minerals — quartz (SiO₂), feldspars, olivine, and carbonates all rely on O²⁻ anions.
Reactive Oxygen Species (ROS)
Partially reduced oxygen species — superoxide (O₂⁻·), hydrogen peroxide (H₂O₂), hydroxyl radical (·OH), and singlet oxygen (¹O₂) — are collectively called reactive oxygen species. ROS play dual roles: at low levels they act as signaling molecules; at high levels they cause oxidative stress, damaging DNA, proteins, and lipids. Antioxidants (vitamins C and E, superoxide dismutase) counter ROS damage.
Summary
Oxygen is a highly reactive nonmetal and the third most abundant element in the universe by mass. With atomic number 8 and symbol O, it belongs to Group 16 (the chalcogens) and Period 2. Oxygen makes up approximately 21% of Earth's atmosphere as the diatomic molecule O₂, and is the most abundant element by mass in Earth's crust, oceans, and the human body. This reference compiles the essential physical constants, electronic structure, isotope data, and chemical properties of oxygen in one place.
How it works
- Browse the atomic identity section for symbol, atomic number, and standard atomic weight.
- Check the electron configuration panel for orbital notation and the interactive shell diagram.
- Toggle the temperature unit (°C / °F / K) on the physical properties card to convert melting and boiling points.
- Review the isotopes table for oxygen-16, oxygen-17, and oxygen-18 data including natural abundance.
- Consult the chemical properties panel for electronegativity, ionization energies, and oxidation states.
- Explore the key facts section for biological roles, industrial applications, and atmospheric significance.
Use cases
- Look up oxygen constants for chemistry homework or exams.
- Verify atomic data when writing lab reports or research papers.
- Reference isotope data for stable isotope labeling or mass spectrometry.
- Check physical properties for engineering applications involving liquid oxygen.
- Teach or learn oxygen chemistry and its essential role in biology and combustion.
- Confirm electron configuration before writing molecular orbital diagrams.
- Quick-reference oxidation states for inorganic or analytical chemistry.
- Review electronegativity and ionization energy for spectroscopy or computational chemistry.