ChlorineThis PowerPoint was brought to you by the the atomic symbol Cl

Discovery

• Chlorine was discovered in 1774 by Swedish chemist Carl Wilhelm

Scheele (1742-86). Scheele mixed pyrolusite (consists primarily of

manganese dioxide (MnO2) with hydrochloric acid (HCl). He found that a

greenish-yellow gas with a suffocating odor "most oppressive to the

lungs" was released. The gas was chlorine. He mistook the gas to be an

oxide of the acid and hence named it “Oxymuriatic Acid”.

• In 1800, Humphry David, identified it as an element and gave it the

name chlorine from its greenish color. [Greek – Chloros means green]

• Chlorine is termed as a Halogen; in Greek Halogen means a salt

producer on account of the fact that all halogens occur as salt.

Occurrence

In Free State

• Chlorine does not occur in the free state due to its highly reactive nature, high

electro negativity and salt forming tendency.

• Chlorine combines with metals and nonmetals forming corresponding chlorides

In Combined State

• Widely distributed in nature as chlorides

• Chlorine occurs commonly both in the Earth's crust and in seawater. Its

abundance in the earth is about 100 to 300 parts per million. It ranks 20 th among

the elements in abundance in the earth. Its abundance in seawater is about 2.6%.

• The most common compound of chlorine in seawater is sodium chloride. Smaller

amounts of potassium chloride also occur in sea water. Carnallite

[KCl.MgCl2.6H2O] and Stassfurt deposits of Magnesium chloride and Sylvine [KCl]

are important minerals in which Chlorine can occur in combined form

Physical Properties

• Diatomic, greenish-yellow gas having a choking, suffocating odour• Highly Electronegative element• Non Metallic element• Highly Reactive Halogen• Chlorine is slightly sour in taste.• Chlorine is a dense gas with a density of 3.21 grams per liter. By comparison,

the density of air is 1.29 grams per liter. • Chlorine changes from a gas into a liquid at a temperature of -34.05°C (-

29.29°F) and from a liquid to a solid at -101.00°C (-149.80°F). • The gas is moderately soluble in water. • It also reacts chemically with water as it dissolves to form hydrochloric acid

(HCl) and unstable oxyacid - hypochlorous acid (HClO).• Chlorine is highly poisonous; it corrodes the inner lining of the respiratory

tract and destroys the mucous membrane. If inhaled in large quantities it can be fatal.

• Liquid Chlorine boils at -34.6 C• Solid Chlorine melts at -202 C

The fine print

• Chlorine is green and actually named after khlôros, the greek word for green.

• Number of Protons/Electrons: 17

• Number of Neutrons: 18

• Classification: Halogen

• Crystal Structure: Orthorhombic

• Density @ 293 K: 3.214 g/cm3

• Atomic Symbol: Cl

• Atomic Weight: 35.453

Chemical Properties

• Chlorine is a very active element. It combines with all

elements except the noble gases.

• The reaction between chlorine and other elements can often

be vigorous. For example, chlorine reacts explosively with

hydrogen to form hydrogen chloride.

• Chlorine is non-combustible; but like oxygen, it helps other

substances bum. Chlorine is a strong oxidizing agent

• Chlorine bleaches vegetable dyes by oxidation

• Chlorine is highly electronegative and a highly reactive

element and reacts with Metals, Non Metals and Hydrogen

Chemical Properties

Burning of Candle in Chlorine

Observation : A burning candle burns in a jar of chlorine with

a reddish yellow flame forming black particles of soot

[carbon] and hydrogen chloride

Reaction of Phosphorous with Chlorine

Observation : A piece of white phosphorous when placed in a

jar of chlorine first melts and later burns

spontaneously forming thick white fumes of

phosphorous trichloride [PCl3] and a small

amount of phosphorous pentachloride [PCl5]

Chlorine : Addition Reactions

Reaction of Metal with ChlorineObservation: a) Metals like Sodium, potassium, magnesium,

copper and antimony in the form of thin foils may catch fire and burn spontaneously in a jar of chlorine forming respective chlorides.

b) Heated metals like iron, aluminium and zinc readily combine with chlorine forming respective chlorides.

Metal Chlorine Product

Sodium (Burning) 2Na + Cl2 2NaCl

Copper Cu + Cl2 CuCl2

Antimony 2Sb + 3Cl2 2SbCl3

Iron (Heated) 2Fe + 3Cl2 2FeCl3

Aluminium 2Al + 3Cl2 2AlCl3

Chlorine : Addition Reactions

Reaction of Nonmetal with ChlorineReaction with SulphurObservation: Dry Chlorine when passed through molten sulphur

forms vapors of sulphur monochloride which condense to give a red liquid

Reaction with HydrogenObservation: Burning Hydrogen burns in chlorine forming

hydrogen chloride. Equal volumes of Hydrogen and Chlorine combine slowly and

silently in diffused sunlight. In direct sunlight the same reaction is explosive.

Non Metal Chlorine Product

Sulphur 2S + Cl2 S2Cl2

Hydrogen H2 + Cl2 2HCl

Position of Chlorine in the Periodic Table

General Group Characteristics – Applied to Chlorine in Group 17

• Physical State : Tendency to form condensed molecules

increases from Chlorine to Iodine. Flourine (Gas); chlorine

(Gas); Bromine (Liquid); Iodine (Solid)

• Electro-negativity : Changes from highly Electronegative to

Least electronegative

• Character : Changes from highly nonmetallic to least non

metallic

• Reactivity : Changes from Highly Reactive to Least Reactive

• Oxidizing Nature : Changes from Very Strong to Mild Oxidizing

agent

Exclusive properties of Chlorine in Group 17

• Greenish yellow in color

• Displaces Bromine and Iodine from Bromides and Iodides

• Forms Hydrides in presence of sunlight without heat or

catalyst

• Strong oxidizing agent

• Bleaches vegetable dyes easily

Arrangement of Electrons in Chlorine

The arrangement of the electrons in chlorine is 2, 8, 7 (i.e. 2 in the first shell, 8 in the second shell and 7 in the third or outer shell). This means that they are not stable, but they need to gain one electron to the outer shell to complete the octet & make the chlorine atom stable.

The arrangement of electron in Chlorine atom is

1s2 2s2 2p6 3s2 3p5. The atomic number of an atom gives the number of protons and hence the number of electrons. Since the atomic number of Chlorine is 17, there are 17 electrons in a chlorine atom.

Order of Filling Sublevels with Electrons in Chlorine Atom

• The number of electrons that can fit into each s subshell is 2 for the first, 6 (2 + 4) for the p subshell and 10 electrons(6 + 4) for the d subshel and so on. The order filling of electrons in different subshells can be obtained by placing diagonal arrows through the subshell pattern, as shown.

Remember:- No heating is required in when potassium permanganate is used as an oxidizing agent in the above method of preparing chlorine.

Preparation of Chlorine

Preparation of Chlorine

Chlorine can be prepared by removing the hydrogen from hydrochloric acid using an oxidizing agent.

Any oxidising agent such as manganese dioxide, lead dioxide, trilead tetroxide, potassium permanganate or potassium dichromate can be used.

Firstly, the oxidising agents are taken in the

round bottomed flask. Concentrated hydrochloric acid is then added through a thistle funnel. This mixture is then heated. The oxygen of the oxidizing agents combines with the hydrogen of the hydrochloric acid leaving behind chlorine i.e. hydrogen is removed from hydrochloric acid. The metallic ions of the oxidising agents combine with part of chlorine to form the respective chlorides.

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