17Cl35.45

Chlorine

Halogens

Very reactive non-metals with seven outer electrons. They form salts with metals.

[Ne] 3s² 3p⁵

Atomic number: 17
Atomic mass: 35.45
Protons: 17
Neutrons: 18 (most common)
Electrons: 17
Shells: 2, 8, 7
State at 25 °C: Gas
Position: Group 17, period 3

Proton (+)Neutron (0)Electron (−)

Discovered byCarl Wilhelm Scheele, 1774Carl Wilhelm Scheele: 6 elements

Scheele made a greenish-yellow gas but thought it was a compound. Humphry Davy proved it was an element in 1810 and named it from the Greek chloros, meaning pale green.

Did you know?

It is a poisonous gas on its own, but safe when locked in salt.
Its name describes its colour.

Where it's found

Table salt
Seawater

What it's used for

Cleaning drinking water
Bleach
PVC pipes

Try it

There's no safe home experiment for Chlorine. Explore it with the animated atom above instead.