Atomic number: 17

Symbol: Cl

Category: non-metal

Density at 25°C: gas

Chlorine is a gas that has a slightly yellowish haze. But it is also very unstable chemically. Even with it self it needs company with itself as Cl2 . As with other reactive elements it tends to be bound up with other elements. In this case sodium is a good example to produce common table salt NaCl. 

A sealed glass tube (ampoule) of chlorine gas. image: adapted from wikipedia

Use, natural applications or common combinations: 

  • Essential to life as Cl- ion
  • Common acid with as HCl
  • Swimming pool cleaning agent ( usually in the form of Trichloroisocyanuric acid with the formula (C3Cl3N3O3) Trichlor for short.

Basic characteristics:

  • Standard atomic weight: [35.446, 35.457] why this variation?
  • Melting point: -101.5 °C
  • Boiling point: -34.04 °C
  • Radioactivity: most are stable
    • trace amounts of 36Cl with half life of  3.01×105 years