Oxygen

Properties

Atomic number

8

Atomic mass

15.999 u

Category

Reactive Nonmetal

Group

16

Period

2

Block

p-block

Electron configuration

[He] 2s² 2p⁴

Phase at STP

Gas

Density

1.429 g/L

Melting point

54.36 K (-218.8 °C)

Boiling point

90.2 K (-182.9 °C)

Electronegativity

3.44

Atomic radius

48 pm

Ionization energy

13.618 eV

Discovery

1774 · Joseph Priestley, Carl Wilhelm Scheele

Compounds you can make with oxygen

Oxygen appears in 52 compounds in our periodic table sandbox. Each one is a real substance with its true chemical formula — combine the right elements in the right ratio below to discover it.

• H₂O

  Water

  The most essential compound for life, covering 71% of Earth’s surface.

• CO₂

  Carbon Dioxide

  The gas you exhale and plants breathe in; a key greenhouse gas.

• CO

  Carbon Monoxide

  A toxic gas produced by incomplete combustion of carbon fuels.

• O₂

  Oxygen Gas

  The breathable form of oxygen — two atoms double-bonded together.

• O₃

  Ozone

  A three-atom form of oxygen that shields Earth from ultraviolet radiation.

• NaOH

  Sodium Hydroxide (Lye)

  A strong base used in soap-making, drain cleaner, and paper production.

• H₂SO₄

  Sulfuric Acid

  A dense, oily acid and one of the most produced industrial chemicals on Earth.

• HNO₃

  Nitric Acid

  A powerful acid used to make fertilizers and explosives.

• Fe₂O₃

  Iron(III) Oxide (Rust)

  The reddish-brown crust that forms when iron reacts with oxygen and water.

• CaCO₃

  Calcium Carbonate

  The mineral in limestone, chalk, marble, eggshells, and seashells.

• CaO

  Calcium Oxide (Quicklime)

  Quicklime, used in cement, steelmaking, and historically in stage "limelight".

• H₂O₂

  Hydrogen Peroxide

  A reactive cousin of water, used as a disinfectant and bleaching agent.

• SO₂

  Sulfur Dioxide

  A pungent gas released by volcanoes and the burning of fossil fuels.

• NO₂

  Nitrogen Dioxide

  A reddish-brown gas that gives smog its color and contributes to acid rain.

• CH₄O

  Methanol

  The simplest alcohol, used as fuel, solvent, and antifreeze.

• C₆H₁₂O₆

  Glucose

  A simple sugar and the primary energy source for living cells.

• C₂H₆O

  Ethanol

  The alcohol found in beverages, also used as fuel and disinfectant.

• Li₂O

  Lithium Oxide

  A white solid used in ceramics and as a component in some glasses.

• MgO

  Magnesium Oxide

  A white mineral used in antacids, supplements, and refractory bricks.

• Al₂O₃

  Aluminium Oxide (Alumina)

  A very hard compound; rubies and sapphires are alumina with trace impurities.

• SiO₂

  Silicon Dioxide (Quartz)

  The main component of sand, quartz, and glass.

• Na₂O

  Sodium Oxide

  A compound used in glassmaking and ceramics.

• ZnO

  Zinc Oxide

  A white powder used in sunscreen, ointments, and paints.

• CuO

  Copper(II) Oxide

  A black solid used in pigments and as a catalyst.

• TiO₂

  Titanium Dioxide

  The brightest white pigment known, used in paint, sunscreen, and food.

• NaHCO₃

  Sodium Bicarbonate (Baking Soda)

  Baking soda — a mild base used in cooking, cleaning, and antacids.

• N₂O

  Nitrous Oxide (Laughing Gas)

  Laughing gas — a mild anesthetic and the propellant in whipped cream.

• H₃PO₄

  Phosphoric Acid

  A mild acid that gives cola its tang and is used in rust removal.

• KOH

  Potassium Hydroxide (Caustic Potash)

  A powerful base used to make soft soaps, biodiesel, and alkaline batteries.

• Ca(OH)₂

  Calcium Hydroxide (Slaked Lime)

  Slaked lime, used in mortar, plaster, and to treat acidic soil and water.

• Na₂CO₃

  Sodium Carbonate (Washing Soda)

  Washing soda — a water softener used in glassmaking, cleaning, and detergents.

• KNO₃

  Potassium Nitrate (Saltpeter)

  Saltpeter, an oxidizer in gunpowder, fertilizer, and food curing.

• NaNO₃

  Sodium Nitrate (Chile Saltpeter)

  A nitrogen-rich salt mined in deserts, used as fertilizer and a food preservative.

• NH₄NO₃

  Ammonium Nitrate

  A high-nitrogen fertilizer that is also a powerful industrial explosive.

• AgNO₃

  Silver Nitrate

  A light-sensitive silver salt used in photography, mirrors, and antiseptics.

• CuSO₄

  Copper(II) Sulfate (Blue Vitriol)

  A brilliant blue salt used as a fungicide, algaecide, and in electroplating.

• MgSO₄

  Magnesium Sulfate (Epsom Salt)

  Epsom salt, dissolved in baths to soothe sore muscles and used in gardening.

• CaSO₄

  Calcium Sulfate (Gypsum)

  Gypsum, the mineral in drywall, plaster of Paris, and blackboard chalk.

• Na₂SO₄

  Sodium Sulfate (Glauber’s Salt)

  A salt used in detergents, glassmaking, and the kraft process for paper.

• KMnO₄

  Potassium Permanganate

  An intensely purple oxidizer used to disinfect water and treat skin conditions.

• C₂H₄O₂

  Acetic Acid (Vinegar)

  The acid that gives vinegar its sour taste and sharp smell.

• H₂CO₃

  Carbonic Acid

  The weak acid formed when CO₂ dissolves in water — the fizz in soda.

• CH₂O

  Formaldehyde

  A pungent gas used to make resins and, in solution, to preserve biological specimens.

• MnO₂

  Manganese Dioxide

  A black mineral used in dry-cell batteries and to color glass.

• Cr₂O₃

  Chromium(III) Oxide

  A durable green pigment used in paints, ceramics, and polishing compounds.

• P₂O₅

  Phosphorus Pentoxide

  A white powder so thirsty for water it’s used to dry gases and liquids.

• UO₂

  Uranium Dioxide

  The black ceramic pressed into the fuel pellets that power nuclear reactors.

• BaSO₄

  Barium Sulfate

  The mineral barite — so insoluble that patients safely drink it as X-ray contrast.

• NiO

  Nickel(II) Oxide

  A green oxide used to color ceramics and glass and in nickel-based battery electrodes.

• Eu₂O₃

  Europium(III) Oxide

  The rare-earth oxide behind the red glow of old TV screens and fluorescent lamps.

• RuO₂

  Ruthenium(IV) Oxide

  The electrode coating that produces most of the world's chlorine.

• In₂O₃

  Indium(III) Oxide

  The base of indium tin oxide (ITO), the invisible conductor coating every touchscreen.

Try it yourself: the oxygen sandbox