Oxygen participates in both biology and heavy industry. Dissolved oxygen supports aerobic life in water, while oxygen gas is used in steel production and metal cutting. Photosynthetic organisms release oxygen, connecting the atmosphere to reactions powered by sunlight and to the chemistry of respiration.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
How does oxygen help change the composition of molten iron during steelmaking?
Oxygen gas
FOLLOW THIS RELATIONSHIP
Identify the starting melt
Molten iron contains carbon and other constituents whose amounts affect the final steel; processing must control composition as well as keep the material hot.
Explore the model (optional)
OFORM → INTERACTION → CONSEQUENCE
Follow the explanation in either direction. These are authored steps, not a physical clock.
Preparation and interpretation were different achievements
Oxygen's discovery involved several investigators and more than one kind of achievement. Scheele prepared the gas before Priestley's better-known 1774 work, but published later. Lavoisier helped reinterpret the evidence and named the element. The sequence shows why preparing a substance, publishing an observation, and explaining its role in combustion should not be collapsed into a simple story of one person discovering everything.
1771
Early preparation
Scheele produced oxygen before publication of his later account.
1774
Experimental evidence published
Priestley prepared and investigated a gas that supported stronger combustion.
Oxygen occurs in the atmosphere as a gas and in compounds throughout water, , and living matter. A large share of its terrestrial presence is chemically bonded rather than free oxygen gas. Different reservoirs therefore need different observations and separation methods to establish their composition.
Oxygen gas reacts with many substances, while oxygen atoms also form part of stable compounds such as water and mineral . Ozone contains the same element in a different molecular form. These examples separate elemental identity from molecular identity and from the behavior of a particular substance.
Each section links its supporting references. Descriptions and diagrams were authored for this atlas. Source checks completed. Source checks dated 2026-09-06.
CITE THIS PAGE
Family labels and the group-3 layout are teaching conventions. A table position does not establish an unknown bulk property. Electronic configurations refer to neutral atoms; ions and material environments require their own account.
Read each reference property together with its units, conditions and the reference information below.
Not yet recorded: electron affinity, second ionization energy, ground-state term symbol, van der waals radius, thermal conductivity, specific heat capacity, electrical resistivity, crystal structure, lattice parameter a, space group, abundance in seawater, abundance in the universe, annual production, supply-risk listing, hazard classification, biological role, cas registry number, pubchem cid, wikidata item. These families are declared and awaiting an ingestion run against the source each names; they are listed here rather than shown as empty rows.
Physical
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Phase at 20 °C
gas
293.15 K, 101.325 kPa
Melting point in K
54.36 K
at standard pressure unless noted
Boiling point in K
90.2 K
101.325 kPa
Density in g/cm³
0.00143 g/cm³
solids and liquids at 293 K; gases at 273 K and 101.325 kPa
Atomic and electronic
Intended reference: Pauling electronegativity scale · Widely tabulated; original in The Nature of the Chemical Bond
Electronegativity in Pauling
3.44 Pauling
Pauling scale
First ionization energy in kJ/mol
1314 kJ/mol
gas-phase neutral atom, ground state
Covalent radius in pm
66 pm
single-bond covalent radius
Common oxidation states
-2
states met in ordinary compounds; not exhaustive
Occurrence and identity
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Abundance in the crust in mg/kg
461000 mg/kg
upper continental crust, mass fraction
Has stable isotopes
Yesderived
Discovery year in CE
1775 CEderived
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity across period 2
O 3.44 Pauling · Oxygen
Electronegativity across period 2. Exact values.
Li
0.98
Be
1.57
B
2.04
C
2.55
N
3.04
O
3.44
F
3.98
Electronegativity down group 16
O 3.44 Pauling · Oxygen
Electronegativity down group 16. Exact values.
O
3.44
S
2.58
Se
2.55
Te
2.1
Po
2
The trend uses the same reference-property values as the periodic table. Elements with no recorded value are left out of the line rather than drawn at zero.
