This document outlines the history, properties, and uses of chlorine. It discusses how chlorine was discovered in 1774 by Carl Scheele and named an element in 1810 by Humphry Davy. Chlorine is a greenish-yellow gas that is highly reactive. It is used as a disinfectant in water treatment and has many industrial applications. The document also details chlorine's physical and chemical properties, electron configuration, common reactions, health effects from exposure, and methods of preparation.

1. Karwan Omer
May 2017

2. Outlines
1- History
2- Introduction
3- Occurrence of chlorine
4- Position of chlorine in the periodic table
5- physical and chemical properties of chlorine
6- Electron configuration and bonding in Chlorine gas
7- Uses of Chlorine
8- Methods for the preparation of chlorine gas
9- Test for the identification chlorine gas
10- Reactions of chlorine
11- Health Effects of Chlorine

3. History
Chlorine was discovered by Carl William Scheele at 1774 in
Sweden. The Origin of name come from the Greek word "chloros"
meaning "pale green “ Chlorine was discovered in 1774 by Carl
William Scheele. He obtained it through the reaction of the mineral
pyrolusite (manganese dioxide, MnO2) with hydrochloric acid (HCl,
then known as muriatic acid).
MnO2(s) + 4HCl(aq) → Cl2(g) + MnCl2(aq) + 2H2O(l)

4. Scheele thought the resulting gas contained oxygen. He did not realize
he had generated a previously unknown chemical element. It was not until
1810 that British scientist , Sir Humphry Davy proposed and confirmed
chlorine to be an element in 1810, and he also named the element.

5. Introduction
Chlorine is the non-metallic chemical element, symbol Cl, Chlorine is a highly
poisonous, greenish yellow gas, about two and a half times as dense as air, and
with a strong, sharp, choking odor. It was, in fact, one of the first poisonous gases
used in warfare—in 1915 during World War I.one of roughly 90 basic building
blocks of matter. Naturally chemically reactive, chlorine’s tendency to combine
with other elements and compounds has been used to produce thousands of
essential products.

6. Chlorine gas
Chlorine is rarely present in nature by itself as elemental chlorine, and
typically exists bonded to other elements in the form of chemical
compounds such as sodium chloride (table salt).

7.  In nature, chlorine is widely distributed over the earth in the form
of the salt (sodium chloride) in sea water. Halite (NaCl) , sylvite
(KCl) and carnallite (MgCl2.KCl.6H2O).
 average concentration of 0.67 oz (19 g) of chlorine in each liter
of sea water, it is estimated that there are some 1016 tons of
chlorine in the world's oceans.
 1016tons of chlorine in the world's oceans. Other compounds of
chlorine occur as minerals
Occurrence of chlorine

8. Chlorine is the 17th element on the periodic table. It is located in period 3
and group 17.
Position of chlorine in the periodic table

9. Physical Properties of chlorine
1- Chlorine is a greenish-yellow gas at room temperature and atmospheric
pressure.
2- Density of chlorine (3.214 g/l) is two and a half times heavier than air 1.27 g/l.
3- Chlorine Is soluble in water. Its aqueous solution is called chlorine water
which consists of a mixture of chlorine, hydrochloric acid (HCl), and
hypochlorous acid (HClO).
4- The boiling point of chlorine is –34.05°C.
5- The melting point of chlorine is –101°C.

10. Chemical Properties of chlorine
1- Oxidation numbers of chlorine aside from the −1 oxidation state are
+1, +3, +4, +5, +6, and +7. in the following chlorine dioxide (ClO2),
chlorine perchlorate (Cl2O4), dichlorine hexoxide (Cl2O6), and
dichlorine heptoxide (Cl2O7)—all highly reactive and unstable
2- the first ionization energy of chlorine is high
3- Chlorine is highly corrosive.
4- Chlorine displaces the heavier, less electronegative halogens, bromine and iodine ,
from compounds. The displacement of bromides, for example, occurs according to the
following equation:
5- Specific mixtures of chlorine and hydrogen can be explosive

11. The electron configuration of a chlorine atom (Cl) is as follows:
1s22s22p63s23p5
[Ne]3s23p5
Electron configuration and bonding in Chlorine gas
A chlorine atom has 7 electrons in its outer shell.

12. Two chlorine atoms will each share one electron to get a full outer
shell and form a stable Cl2 molecule.
This is a picture of the shared electrons making a covalent bond
in a chlorine molecule. Chlorine is a simple molecule.
By sharing the two electrons where
the shells touch each chlorine atom
can count 8 electrons in its outer
shell.

13.  Chlorine used as oxidizing agent and in substitution reactions. And for
the manufacture of chlorates and it is important in organic
chemistry, forming compounds such as chloroform, carbon
tetrachloride, polyvinyl chloride, and synthetic rubber.
 Chlorine gas is itself very poisonous, and was used as a chemical
weapon during the War.
 Chlorine kills bacteria – it is a disinfectant. It is used to treat drinking
water and swimming pool water.
 Pharmaceuticals: Chlorine chemistry is used in the production of a
large proportional of all prescription drugs.
Uses of Chlorine

14.  Add concentrated hydrochloric acid dropwise onto a small quantity
of potassium permanganate crystals (in a flask). Collect the
chlorine gas by upward displacement of air in a hood .
Reaction
2 KMnO4 + 16 HCl ==> 2 MnCl2 + 2 KCl + 8 H2O + 5 Cl2
Methods for the Preparation of chlorine gas

15.  Chlorine may also be obtained by heating manganese dioxide with
concentrated hydrochloric acid
MnO2 + 4HCl  MnCl2+2H2O +Cl2
On industrial scale Cl2 is obtained by the electrolysis of aqueous solution
of NaCl called Brine.
2NaCl + 2H2O  Cl2+H2 + 2NaOH

16. Tests for the identification chlorine gas
 Chlorine gas, Cl2(g) is green-yellow in color.
Chlorine has a characteristic sharp, choking smell.
 It also makes damp blue litmus paper turn red.
 Chlorine gas is extremely soluble in water. It dissolves to
form hydrochloric acid, a strong acid, pH = 1

17. 1- Reaction of Chlorine with Sodium Hydroxide
Chlorine reacts with a hot solution of Sodium Hydroxide to give a mixture of
Sodium Chloride and Sodium Chlorate.
3Cl2 + 6 NaOH ==> 5 NaCl + NaClO3 + 3 H2O
2- Reaction with water H2O + Cl2 ==> HCl + HClO
The Hypochlorous Acid, HClO, is not very stable and the solution readily
decomcomposes, especially when exposed to sunlight, yielding Oxygen.
2 HClO ==> 2 HCl + O2
Reactions of chlorine

18. 3- Oxidising Reaction of Chlorine
Chlorine is a strong oxidising agent. Chlorine oxidises Iron (II) Chloride, FeCl2, to the salt
containing Iron in the higher oxidation state Iron (III) Chloride, FeCl3. This is possible
because Iron has a variable valency.
2 FeCl2 + Cl2 ==> 2 FeCl3
4- Chlorine displaces the less electronegative Bromine and Iodine from their respective
salts.
Cl2 + 2 KBr ==> 2 KCl + Br2
5- Chlorine removes Hydrogen from the hydrides of non-metals, forming Hydrogen
Chloride, and leaving the non-metal element.
Cl2 + H2S ==> 2 HCl + S

19. 6- Reaction of Chlorine with Hydrogen
A mixture of Chlorine and Hydrogen explodes when exposed to sunlight to give
Hydrogen Chloride. In the dark, no reaction occurs, so activation of the reaction by
light energy is required.
Cl2 + H2 ==> 2 HCl
7- Halogenation of Organic compounds
CH4 + Cl2 CH3Cl + HCl
Unsaturated compounds, especially alkenes and alkynes, add halogens:
CH2 = CH2 + Cl2 CH2Cl-CH2Cl

20. Health Effects of Chlorine Exposure, Concentration Health Effects
(ppm in air) summarized in table bellow:
Health Effects of Chlorine
Health EffectsConcentration (ppm in air)
Mild mucous membrane irritation1-3 ppm
Upper respiratory tract irritation5-15 ppm
Immediate chest pain, vomiting, shortness of breath (dyspnea)
and cough
30 ppm
Inflammation of lung tissues (toxic pneumonitis) and fluid
accumulation (pulmonary edema)
40-60 ppm
Death within 30 minutes430 ppm
Death within a few minutes1,000 ppm

21. References
1- Christe. K and Scheider .S (2016). Encyclopedia brittanica [ online] Available at:
https://www.britannica.com/science/chlorine/Physical-and-chemical-properties
[Accessed 21 April 2017].
2- Rutala, W.A. and Weber, D.J., 1997. Uses of inorganic hypochlorite (bleach) in health-care
facilities. Clinical microbiology reviews, 10(4), pp.597-610.
3- Tundo, P., He, L.N., Lokteva, E. and Mota, C., 2016. Chemistry Beyond Chlorine.
4- Stringer, R. and Johnston, P., 2001. Chlorine and the environment: An overview
of the chlorine industry. Springer Science & Business Media.