chlorine
TRANSCRIPT
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.
http://www.youtube.com/watch?v=QkDXD468XOY