Chlorine (17)

Chlorine is a greenish yellow gas which combines directly with nearly all elements. Chlorine is a respiratory irritant, hence its use as a choking agent in WWI and WWII. The gas irritates the mucous membranes and the liquid burns the skin. As little as 3.5 ppm can be detected as an odor, and 1000 ppm is likely to be fatal after a few deep breaths. It was used as a war gas in 1915. It is not found  in a free state in nature, but is found commonly as NaCl (solid or seawater).

•Name: Chlorine
•Symbol: Cl
•Atomic number: 17
•Atomic weight: 35.453
•Standard state: gas at 298 K
•CAS Registry ID: 7782-50-5
•Group in periodic table: 17
•Group name: Halogen
•Period in periodic table: 3
•Block in periodic table: p-block
•Color: yellowish green
•Classification: Non-metallic

Historical information

Chlorine was discovered by Carl William Scheele at 1774 in Sweden. Origin of name: from the Greek word "chloros" meaning "pale green". Chlorine was discovered in 1774 by Carl Wilhelm Scheele. He obtained it through the reaction of the mineral pyrolusite (manganese dioxide, MnO2) with hydrochloric acid (HCl, then known as muriatic acid). Scheele thought the resulting gas contained oxygen. Sir Humphry Davy proposed and confirmed chlorine to be an element in 1810, and he also named the element.

Physical properties

•Melting point: 171.6 [or -101.5 °C (-150.7 °F)] K
•Boiling point: 239.11 [or -34.04 °C (-29.27 °F)] K
•Density of solid: 2030 kg m-3

Orbital properties

•Ground state electron configuration: [Ne].3s2.3p5
•Shell structure: 2.8.7
•Term symbol: 2P3/2

Isolation

It is rarely necessary to make chlorine in the laboratory as it is readily available commercially in cylinders. Chlorine is found largely in seawater where it exists as sodium chloride. It is recovered as a reactive, corrosive, pale green chlorine gas from brine (a solution of sodium chloride in water) by electrolyis. Electrolysis of molten salt, NaCl, also succeeds, in which case the other product is sodium metal rather than sodium hydroxide.

Na+ + Cl- + H2O → Na+ + 1/2Cl2 + 1/2H2 + OH-

In the laboratory under carefully controlled conditions, chlorine can be made by the action of an oxidizing agent such as manganese dioxide, MnO2, upon concentrated hydrochloric acid - the same reaction used by Scheele in 1774 when discovering chlorine.

MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O

Interesting Facts:

1. Chlorine's Atomic number is 17

2. Chlorine's melting point is -100.98 °C

3. Chlorine's boiling point is 34.6 °C

4. Chlorine was first discovered by Carl Wilhelm Scheele in Sweden back in 1774

5. Chlorine is a member of the halogen group and combines with nearly all the other elements.

6. Both in gas form as well as in liquid, Chlorine is an irritant and will negatively affect the respiratory system in gas form while it can burn your skin when in liquid form.

7. More than a few breaths of Chlorine in concentrations of 1000ppm will typically kill you.

8. Chlorine in gas form is a yellow-greenish color.

9. Chlorine containing molecules in the upper atmosphere have been implicated in destruction of our ozone layer.

10. Sodium Chloride, otherwise known as rock schalt, is the most common compound containing Chlorine and has been around and in use dating back to 3000 B.C