Chlorine
Reactive Nonmetal
Chlorine (Cl) is a chemical element with atomic number 17, classified as a reactive nonmetal. At room temperature it is a gas. It was discovered in 1774 by Carl Wilhelm Scheele.
Properties
- Atomic number
- 17
- Atomic mass
- 35.45 u
- Category
- Reactive Nonmetal
- Group
- 17
- Period
- 3
- Block
- p-block
- Electron configuration
- [Ne] 3s² 3p⁵
- Phase at STP
- Gas
- Density
- 3.214 g/L
- Melting point
- 171.65 K (-101.5 °C)
- Boiling point
- 239.11 K (-34.0 °C)
- Electronegativity
- 3.16
- Atomic radius
- 79 pm
- Ionization energy
- 12.968 eV
- Discovery
- 1774 · Carl Wilhelm Scheele
Common uses
Water purification, bleach, PVC plastic, table salt
Did you know?
Poisonous gas that saves millions of lives by disinfecting drinking water.
Compounds you can make with chlorine
Chlorine appears in 10 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.
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NaCl
Sodium Chloride (Table Salt)
Common table salt, formed when a violently reactive metal meets a poisonous gas.
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HCl
Hydrogen Chloride
Dissolved in water it becomes hydrochloric acid, found in your stomach.
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KCl
Potassium Chloride
A salt substitute and essential nutrient, also used in fertilizers.
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CaCl2
Calcium Chloride
A salt used for de-icing roads and as a drying agent.
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AgCl
Silver Chloride
A light-sensitive salt that was the basis of photographic film.
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NH4Cl
Ammonium Chloride
A salt used in batteries, fertilizer, and as a food additive (salty licorice).
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CCl4
Carbon Tetrachloride
A dense, non-flammable liquid once used in fire extinguishers and dry cleaning.
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AlCl3
Aluminium Chloride
A workhorse catalyst in petroleum refining and organic synthesis.
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FeCl3
Iron(III) Chloride
A dark salt used to treat wastewater and to etch copper circuit boards.
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BaCl2
Barium Chloride
A soluble barium salt used in labs to test for sulfate and to give fireworks a green flash.