2. Chlorine

2.1 General characteristics of the element chlorine

• Diatomic chlorine was discovered in 1774 by Swedish chemist Carl Wilhelm Scheele, by reacting a few drops of hydrochloric acid (then called "muriatic") with pyrolusite (MnO ₂ ): he obtained a dense, greenish gas, which was later named chloric gas by Sir Humphrey Davy in 1810 (from the Greek khlôros meaning "pale green").

  Box 2: Chlorine

  Symbol: Cl

  Atomic number: 17

  Atomic mass: 35.453 (often rounded to 35.5)

  Chlorine is the 20th most abundant element in the earth's crust (see the main properties of chlorine in Box 2);...