Introduction Occurrence Peculiar Behavior of Fluorine and ... · are good oxidizing agents. Usually they react with metals and oxidize them hence reducing themselves. 2Na + Cl 2 Æ

Introduction Occurrence

Peculiar Behavior of Fluorine and Oxidizing Properties Compounds of Halogens, Hydrides, Oxides and Oxyacids

Uses of Halogens & Their Compounds Noble Gases, Their Compounds & Applications

4/17/2020 1 AAFAQ ACADEMY

Introduction to Halogens Halogen: A composite of two words, i.e., hals means salt and

gennan means forming or generating, so halogens means salt forming.

Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I) and Astatine (At)

Very reactive non-metals

Fluorine (F), Chlorine (Cl), Bromine (Br) and Iodine (I) are normal elements while Astatine (At) is radioactive element with half life of 8.3 hours.

Halogens exist as diatomic state, i.e., F2, Cl2, Br2 and I2.

F2 & Cl2 are pale yellow and greenish yellow gases, respectively, Br2 is reddish brown liquid and I2 is greyish black solid.


Introduction to Halogens Irritating Odour and attack skin

Bromine cause severe burns that heal slowly

General Electronic Configuration is ns2.np5

Ionization energy is of the following order F>Cl>Br>I

Electron affinity is of following order F<Cl>Br>I

Electrode potential is of following order

Iodine being larger molecule has largest attraction for each other through London Dispersion Forces.

F2 Cl2 Br2 I2

Standard Electrode Potential (E°) X2 + 2e- 2X- +2.87V +1.36V +1.07V +0.54V


Occurrence Being very reactive so never exist in free state

Binary compounds Halides

Halides: Water soluble and found in sea, salt lakes and underground salt beds like Khewra in Pakistan


Fluorine Chlorine

Fluorospar CaF2 Halite NaCl

Cryolite Na3AlF6 Carnallite KCl.MgCl2.6H2O

Fluoroapatite Ca5(PO4)3F

Bromine Iodine

Brine Wells and Sea Water

NaBr, KBr, MgBr2 Chile Brine Wells NaIO3 & NaIO4

Peculiar Behaviour of Fluorine Fluorine differ from rest of halogens due to following reasons: i. Small size of F – atom and of F- – ion. ii. High first ionization energy and electronegativity. iii. Low dissociation energy of F2 – molecule as compared to Cl2

and Br2. iv. Restriction of the valence shell to an octet. v. Direct combination with inert gases. Small size of F – atom and of F- – ion better overlap of orbitals

and shorter & stronger bonds with elements other than O, N and itself. Ionic fluorides have higher lattice energies than the other halides

that is the reason of insolublity of fluorides of Mg, Ca, Sr, Ba & Lanthanides.

4/17/2020 AAFAQ ACADEMY 5

Peculiar Behaviour of Fluorine Due to low dissociation energy of F2 molecule, it is

highly reactive while others react relatively slowly under similar conditions. Fluorides are more stable with respect to dissociation into elements.

Due to restriction of valence shell to an octet, many fluoro compounds show inertness, e.g., CF4 and SF6. Due to restriction to octet of 2nd shell, f luorine remains restricted to -1 oxidation state.

Fluorine is the only halogen that react directly with noble gases like Kr, Xe and Rn forming their fluorides.


Oxidizing Properties

Relative Reactivity of Halogens as Oxidizing Agents

Halogens have strong tendency towards accepting electron and get reduced themselves and hence they are good oxidizing agents. Usually they react with metals and oxidize them hence reducing themselves.

2Na + Cl2 2Na+Cl-

Oxidizing power of halogens decrease down the group. The order of decreasing power as oxidizing agent is F2>Cl2>Br2>I2.


Oxidizing Properties Factors affecting Oxidizing Power of Halogens i. Energy of Dissociation ii. Electron Affinity of Atoms iii. Hydration Energy of ions iv. Heat of Vapourization (for Br2 and I2) Halogen with low dissociation energy, high electron

affinity and a higher hydration energy will have a high oxidizing power and vice versa.

Hence a halogen above in the group can replace the halogen lower in the group from a salt due to its more stronger oxidizing power.


Oxidizing Properties F2 Cl2 Br2 I2

Standard Electrode Potential (E°) X2 + 2e- 2X- +2.87V +1.36V +1.07V +0.54V


F2 + 2e- 2F- E° = 2.87V 2Cl- Cl2 + 2e- E° = -1.36V F2 + 2Cl- Cl2 + 2F- E° = +1.51V

Hence, Chlorine can replace Bromide ion from its salt and Bromine can replace Iodide from its salt but opposite of both processes in impossible.

Cl2 + 2NaBr 2NaCl + Br2

Br2 + 2KI 2KBr + I2

F2 & Cl2 can oxidize various colour dyes to colourless substances, e.g., litmus & universal indicators can be declourized when exposed to F2 & Cl2. Chlorine is an excellent bleaching agent.

Compounds of Halogens Hydrides (Hydrogen Halides, HX)

Halogens react with hydrogen to yield hydrides. Order of reactivity among halogen is F2>Cl2>Br2>I2.

H2(g) + F2(g) 2HF(l)

H2(g) + Cl2(g) 2HCl(g)

H2(g) + Br2(g) 2HBr(g)

H2(g) + I2(g) 2HI(g)

Direct reaction is only used for preparation of HCl(g) and HBr(g).


Explosive Violence

Sunlight

High Temp.

High Temp.

Compounds of Halogens HF & HCl can also be prepared by reaction of concentrated sulphuric acid on fluorides and chlorides, but analogous reactions with bromides and iodides results in partial oxidation of hydrogen halide to free halogen.

CaF2(s) + H2SO4(aq) CaSO4(aq) + 2HF(l)

2NaCl(s) + H2SO4(aq) Na2SO4(aq) + 2HCl(g)

2KBr(s) + H2SO4(aq) K2SO4(aq) + 2HBr(g)

2KBr(s) + 2H2SO4(aq) K2SO4(aq) + Br2(l) + SO2(g) + H2O(l)

2NaI(s) + H2SO4(aq) Na2SO4(aq) + 2HI(g)

2NaI(s) + 2H2SO4(aq) Na2SO4(aq) + I2(s) + SO2(g) + H2O(l)


Properties of Hydrogen Halides HF is a colourless volatile liquid whereas other hydrogen

halides (HCl, HBr & HI) are colourless gases at room temperature.

All fumes in moist air.

Very strong irritants.

HF attacks glass and dissolves it. It is an excellent solvent. Handled in Teflon (PTFE, Polytetrafluoro-ethylene) container or if absolutely dry then in copper or stainless steel container under vacuum. Strong hydrogen bonding among its molecules because of which it exists as liquid.


Properties of Hydrogen Halides Due to absence of three dimensional network in HF as in

H2O, the density of HF is lower than that of H2O.

In vapour phase, the HF molecules associate in hexamers.

6HF (HF)6

Chain polymers of HF are also known under certain conditions.

Chains & rings of HF also exist in vapour phase


Some Physical Properties of Hydrogen Halides Physical Properties HF HCl HBr HI

Melting Point (°C) -83.8 -114.2 -86.9 -50.8

Boiling Point (°C) 19.5 -85.0 -66.7 -35.3

Heat of Fusion at M.P. (kJ.mol-1), ΔH°f 4.58 1.99 2.41 2.87

Heat of Vaporization at B.P. (kJ.mol-1) , ΔH°v 30.3 16.2 17.6 19.7

Heat of Formation (kJ.mol-1) , ΔH°f -270.0 -92.0 -36.0 +26.0

Bond Energy (kJ.mol-1) 566 431 366 299

Bond Length in HX (pm) 92 128 141 160

%age Dissociation into elements @ 1000°C 0 0.014 0.5 33

Dipole Moment (Debye) 1.8 1.1 0.8 0.4


M.P., B.P., Heat of fusion and Heat of Vaporization increase from HCl to HI. HF has exceptionally high values of all these due to hydrogen bonding.

Properties of Hydrogen Halides Decrease in volatility from HCl to HI is due to increase in

Van der Waal’s forces related to polarizability of atoms. The decrease of the values of dipole moment from HF to HI

is due to Debye forces which play vital role in intermolecular binding of heavier molecules.

Very high bond energy in HF is due to larger electronegativity difference. This bond strength clarify the ease of dissociation of HI at 1000°C.

Order as reducing agent is HF < HCl < HBr < HI

HI is strong reducing agent 2HI + S H2S + I2


Properties of Hydrogen Halides In water, hydrogen halides give hydrofluoric acid,

hydrochloric acid, hydrobromic acid and hydroiodic acid which ionize as

HX H+ + X-

Ionization of HF is limited

HCl, HBr & HI are very strong acids.

Order of acid strength among halogen acids is as follows

HF < HCl < HBr < HI


H2O

Oxides of Halogens Halogens don’t react directly with oxygen. Using some other methods, following oxides of halogens have been prepared.


Oxides of Halogens

Fluorine Chlorine Bromine Iodine

Oxygen Difluoride OF2

Dichlorine Monoxide Cl2O

Dibromine Monoxide Br2O

Iodine Tetraoxide I2O4

Dioxygen Difluoride O2F2

Chlorine Dioxide ClO2

Bromine Dioxide BrO2

Iodine Iodate I4O9

Trioxygen Difluoride O3F2

Chlorine Hexaoxide Cl2O6

Dibromine Trioxide Br2O3

Iodine Pentaoxide I2O5

Chlorine Heptaoxide Cl2O7

Oxides of Fluorine Trioxygen Difluoride O3F2

Prepared by electric discharge of mixture of Oxygen & Fluorine.

3O2 + 2F2 2O3F2

At 363°C, it is dark red viscous liquid. At 350°C, it solidifies to reddish brown solid. It decomposes to yield O2F2 and O2.

2O3F2 2O2F2 + O2 O3F2 also react with F2 in presence of electric discharge to produce O2F2.

2O3F2 + F2 3O2F2


Electric Discharge

Electric Discharge

Oxides of Chlorine Generally Unstable

No direct reaction between chlorine and oxygen

Excellent bleaching agents for wood and paper-pulp

Used for water treatment

Chlorine Dioxide, ClO2

Pale yellow gas prepared by reducing NaClO3 with NaCl, SO2 or CH3OH.

2NaClO3+2NaCl+2H2SO4 2ClO2+Cl2+H2O+2Na2SO4

or

2ClO3-+2Cl-+4H+ 2ClO2+Cl2+H2O


Oxides of Chlorine ClO2 can also be prepared by action of Conc. H2SO4 on KClO3, but this reaction is very violent. To control the rate of this reaction, oxalic acid is added.

2KClO3+H2C2O4+H2SO4 K2SO4+2H2O+2CO2+2ClO2

On heating ClO2 explodes to Cl2 and O2.

2ClO2 Cl2 + 2O2

ClO2 is water soluble

Stable in dark

Decompose slowly in water to HCl and HClO3.

Paramagnetic

Used as antiseptic, purification of water and bleaching cellulose.


Δ

Oxides of Chlorine Chlorine Heptaoxide (Cl2O7)

Cl2O7 is an anhydride of perchloric acid (HClO4). It is obtained by reaction of HClO4 with P2O5 at −10°C.

HClO4 + P2O5 Cl2O7 + 2HPO3

Oxides of Bromine

Oxides of Bromine are dark volatile liquids having low thermal stability.

Bromine Monoxide (Br2O)

Prepared by reaction of bromine vapours with mercuric oxide at 50°C or by reaction of bromine with suspension if mercuric oxide at room temperature.

HgO + 2Br2 HgBr2 + Br2O

Stable in dark in CCl4 at −20°C & has oxidizing properties.


−10°C

50°C or −20°C in CCl4

Oxides of Iodine Out of all oxides of iodine only iodine pentoxide (I2O5) is

important. The other compounds, I2O4 and I2O9 are salt like and are considered to be iodine-iodates.

Iodine Pentoxide (I2O5)

It is prepared by heating iodic acid at 240°C

2HIO3 I2O5 + H2O


240°C

White crystalline solid Stable up to 300°C. Polymeric structure. Insoluble in organic solvents. React with water to form iodic

acid

I2O5 + H2O 2HIO3

Reacts with H2S, HCl & CO as an oxidizing agent. Used for quantitative determination of CO. 5CO + I2O5 I2 + 5CO2

5H2S + I2O5 I2 + 5H2O

Reactions of Chlorine with Cold & Hot NaOH These are disproportionation reactions in which same substance

undergo oxidation & reduction.

In cold state (at 15°C), chlorine reacts with NaOH(aq) to form sodium hypochlorite and sodium chloride.

2NaOH(aq) + Cl2(g) NaCl(aq) + NaClO(aq) + H2O(l)

If the same reaction is carried out in hot state (at 70°C), NaClO(aq) decompose to NaCl(aq) and NaClO3(aq).

(2NaOH(aq) + Cl2(g) NaCl(aq) + NaClO(aq) + H2O(l) ) × 3

3NaClO(aq) 2NaCl(aq) + NaClO3(aq)

6NaOH(aq) + 3Cl2(g) 5NaCl(aq) + NaClO3(aq) + 3H2O(l)


15°C

70°C

Oxyacids Oxygen containing halogen acids are termed as Oxyacids.

Stable oxyacids of Cl, Br & I are found to exist in aqueous phase only or in salt form.

HOF has recently been prepared but is highly unstable.


Ox. State

Formula of Oxyacids of Halogens General Names

Chlorine Bromine Iodine Oxyacids Salts of Oxyacid

+1 HClO HBrO HIO Hypohalous Acid Hypohalite

+3 HClO2 Halous Acid Halite

+5 HClO3 HBrO3 HIO3 Halic Acid Halate

+7 HClO4 HIO4 Perhalic Acid Perhalate

Oxyacids Hal means Chlor, Brom & Iod.

Halogen atom is at central position to which O – atoms are attached through polar covalent bonds.


Ox. State +1 +3 +5 +7

Chlorine HClO HClO2 HClO3 HClO4

Bromine HBrO HBrO3

Iodine HIO HIO3 HIO4

Thermal Stablility Increase

Oxidizing Power Decrease

Acidic Strength Increase

Perchloric Acid Perchloric Acid is obtained as aqueous solution by the reaction of

KClO4(s) with Conc. H2SO4(aq) by distillation under reduced pressure. KClO4(s) + H2SO4(aq) KHSO4(s) + HClO4(aq)

HClO4 is colourless & hygroscopic liquid at room temperature. m.p. or f.p. is −112°C and b.p. is 90°C with decomposition. Cold and dilute HClO4 is a weak oxidizing agent. Hot and concentrated HClO4 is a strong oxidizing agent. Excellent dissolving power due to its oxidizing strength. HClO4 is strongest among all available acis. Decompose explosively on heating that is why it is stored as 67%

aqueous solution. React violently with organic substances. A valuable laboratory reagent.


Δ Reduced Pressure

Bleaching Powder Prepared by the reaction of Ca(OH)2(s) with Cl2(g) in accordance with

following reaction… Ca(OH)2(s) + Cl2(g) Ca(OCl)Cl(s) + H2O(l)

There are 2 methods for preparation of Bleaching Powder. 1. Hasenclever Method (Old Method) 2. Beckmann’s Method (Modern Method)

1. Hasenclever Method The apparatus used in this method consists of 4 – 8 iron cylinders

placed one above the other horizontally. They are interconnected and provided with stirrers. Slacked lime, Ca(OH)2(s), is added through a hopper in upper cylinder

and transported from one cylinder to other with rotating stirrers. Chlorine, Cl2(g), is introduced from the lowest cylinder rises up and

react with slaked lime to form bleaching powder, which is collected through an outlet in lowest cylinder.


40°C

Bleaching Powder 2. Beckmann’s Method

A cast iron tower with 8 horizontal shelves is used, shelf consists of rotating rake.

Powdered slaked lime is introduced through hopper at the top with compressed air & chlorine from the base of tower.

Rotating rakes push down the slaked lime while chlorine rises up.

Reaction between slaked lime & chlorine produces bleaching powder that is collected at the bottom.

Apparatus works on counter – current process where reactants are completely consumed.


Bleaching Powder Properties of Bleaching Powder Yellowish white powder, with strong smell of chlorine, so, stored in air

tight containers to avoid loss of chlorine.

In water, it ionizes as Ca(OCl)Cl(s) Ca(aq)2+ + OCl(aq)

− + Cl(aq)−

React with dilute acids to give hypochlorous acid.

2Ca(OCl)Cl + H2SO4 CaSO4 + CaCl2 + HClO

React with an excess of dilute acid or with strong (Conc.) acids releases chlorine.

Ca(OCl)Cl + H2SO4 CaSO4 + H2O + Cl2(g)

The amount of chlorine liberated is called “available chlorine”. The activity of bleaching powder is determined in terms of available chlorine. Average percentage of available chlorine is 35 – 40%.


H2O

Bleaching Powder Bleaching action of bleaching powder is due to its oxidizing character.

Oxidizes halogen acids (HCl, HBr or HI) to produce halogen.

Ca(OCl)Cl + 2HCl CaCl2 + H2O + Cl2

Oxidizes ammonia (NH3(g)) to nitrogen

3Ca(OCl)Cl + 2NH3 3CaCl2 + 3H2O + N2

Reacts with carbon dioxide to yield calcium carbonate & chlorine.

Ca(OCl)Cl + CO2 CaCO3 + Cl2


Uses i. Laboratory preparation of

chlorine & oxygen ii. Manufacture of chloroform. iii. As a disinfectant & water

sterilization

iv. Making unshrinkable wool v. Bleaching cotton, linen & paper

pulp (delicate fabrics are avoided bleaching as they are damaged by chlorine).

Commercial Uses of Halogens & their Compounds

Fluorine:

Used for preparation of freons, i.e., chlorofluorocarbons, e.g., CCl2F2, CClF3, etc. Freons used as refrigerants & aerosol propellants.

Used for preparation of Teflon®, (CF2 – CF2)n. A polymerized tetrafluoro ethylene compound. A valuable plastic which resists the action of oxidants, acids & alkalis. Used to make corrosion free parts of machinery, coating electrical wires and for coating non-stick cooking ware.

A compound of fluorine, halothane,

is used as an anesthetic.

Fluoride is used in toothpastes as protective coating on tooth.



Chlorine:

Used for manufacturing of bleaching powder, used as disinfectants in swimming pools & water treatment plants.

Used in manufacture of antiseptic, insecticides & herbicides.

Used in manufacture of hydrochloric acid, a cheapest industrial acid.

Used in manufacturing of Polyvinyl Chloride (PVC) plastics.

Used in manufacturing of solvents like chloroform (CHCl3) and carbon tetrachloride (CCl4).



Bromine:

Used for preparation of Ethylene Dibromide (C2H4Br2), added to leaded gasoline to save engines from lead oxide & lead sulphate deposits.

Used as disinfectant as tincture iodine and pain reliever IODEX®.

Used as fungicide, germicide.

Silver Bromide was used in B & W photography in past.

Iodine:

Diet with insufficient iodine leads to enlargement of thyroid glands (Goiter). Sodium or Potassium Iodide is added to common salt to make it iodized salt (about 15mg/kg).


Noble Gases Zero Group Elements or Elements of Group VIIIA, i.e., Helium

(He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe) & Radon (Rn) also termed as Noble Gases or Rare Gases.

Colourless, Odourless, Monoatomic Gases which can be liquefied & solidified.

About 1% in atmosphere.

General electronic configuration as ns2.np6.

Isolation of Noble Gases from Air:

Isolated from air either by fractional distillation or by some other chemical method.

The principal commercial source of Ne, Ar, Kr & Xe is air.



Helium Helium is present on earth as a result of radioactive decay. After hydrogen, it is second most abundant element in the universe. α – particles are doubly charged helium ion, i.e., He2+. Extracted economically from certain natural gases by liquefaction

method.

Neon 1/65000th part of the atmosphere. Isolated from liquefaction of air. Used in discharge tube for orange red glow. Among all noble gases the glow of discharge of neon is most intense Liquid neon has 40 times more refrigeration capacity than liquid

helium.


Argon Colourless and odourless. Inert and forms no true chemical compound. By-product of liquefaction of air.

Krypton Trace amounts of krypton in air. Colourless, odourless & fairly expensive gas. Brilliant green & orange spectral lines. Krypton difluoride (KrF2) is prepared by different methods.

Xenon Very little amount in air (0.08ppm). Obtained as by-product of fractional distillation of air. Commercially available in cylinders with high pressure. Directly react with fluorine but not with water. Highly soluble in water to the extent of 110cm3.dm−3. at 20°C.


Radon Radon is α – decay product of radium. It is obtained from same

source. Ra226 Rn222 + He4

Very small extent in air and cannot be obtained as by-product from liquefaction of air.

Common Characteristics of Noble Gases General electronic configuration as ns2.np6 (except He – 1s2). All of them have high ionization energy due to complete doublet or

octet in valence shell. Low b.p., He has lowest value of b.p. among all elements. b.p. of

noble gases increase down the group. Due to complete valence shell, they have very weak intermolecular

forces, i.e., London’s dispersion forces. That’s why values of b.p., m.p. and ΔHv° are very low.

Compounds of Xenon Reacts directly with fluorine.

Oxidation states of Xenon in its compounds range from +2 to +8.

Compounds of Xenon are stable & can be obtained in large quantities.


Ox. State of Xe Compound Physical State Melting Point °C

+2 XeF2 Colourless Crystals 140


XeOF2 Colourless Crystals 90


XeOF4 Colourless Liquid − 28

XeO3 Colourless Crystals 25 Explodes

+8 XeO4 Colourless Gas − 39.9 Explodes on warming

Fluorides of Xenon Three known fluorides of Xenon are XeF2, XeF4 and XeF6.

Xenon Difluoride (XeF2)

Prepared by direct reaction of Xe with F2. Reaction completes in 8 hours.

Xe + F2 XeF2

Must be removed immediately from the reaction zone otherwise it will further react with F2 to yield higher fluorides, i.e., XeF4.

XeF2 + F2 XeF4

Crystalline Solid

Stored in Nickel vessels.

Mild fluorinating agent.



Xenon Tetrafluoride (XeF4)

Prepared by heating mixture of Xe & F2 in 1:5 ratio in a nickel container at 6 atm pressure for few hours.

Xe + 2F2 XeF4

Must be removed immediately from the reaction zone otherwise it will further react with F2 to yield higher fluorides, i.e., XeF6.

XeF4 + F2 XeF6

Crystalline Solid Stored in nickel vessels. Strong fluorinating agent.

Ni

6 atm

Ni

6 atm


Xenon Hexafluoride (XeF6) Preparation needs more severe conditions. Xe & F2 is taken in a

ratio of 3:20 in stainless steel vessel and heated to 300°C & 50 atm pressure.

Xe + 3F2 XeF6

Conversion ratio is more than 95%. Crystalline & colourless Solid. Yellow in liquid & gaseous forms.

Chemical Properties of Xenon Fluorides Fluorides of Xenon can be reduced with hydrogen at 400°C

producing Xenon & hydrofluoric acid. XeF2 + H2 Xe + 2HF XeF4 + 2H2 Xe + 4HF XeF6 + 3H2 Xe + 6HF

Stainless Steel

300°C & 50 atm

400°C

400°C

400°C


Xenon tetrafluoride (XeF4) is a good fluorinating agent and is used to prepare metal fluorides.

XeF4 + 2Hg Xe + 2HgF2

React with ammonia (NH3) with explosive violence. 3XeF4 + 4NH3 3Xe + 12HF + 2N2

Hydrolysis of XeF6 with small amount of water gives XeOF4. XeF6 + H2O XeOF4 + 2HF

Xenon Oxyfluorides Xenon oxytetrafluoride (XeOF4) is formed by reaction of XeF6

with silica (SiO2). 2XeF6 + SiO2 2XeOF4 + SiF4

Colourless volatile liquid. Stored in nickel vessels.


XeOF4 Reacts with H2O to give XeO3. XeOF4 + 2H2O XeO3 + 4HF

Xenon oxydifluoride (XeOF2) is obtained by reaction of Xenon with oxygen difluoride (OF2).

Xe + OF2 XeOF2

Oxides of Xenon 1. Xenon trioxide (XeO3) 2. Xenon tetraoxide (XeO4)

1. Xenon trioxide (XeO3) Xenon trioxide (XeO3) is obtained from hydrolysis of XeF6.

XeF6 + 3H2O XeO3 + 6HF Crystalline solid. Explodes at low temperature.


2. Xenon tetraoxide (XeO4) Formed by displacement reaction of barium or sodium perxenate

(Ba2XeO6 or Na4XeO6) with conc. sulphuric acid (H2SO4). Ba2XeO6 + H2SO4 XeO4 + 2BaSO4 + 2H2O Na4XeO6 + H2SO4 XeO4 + 2Na2SO4 + 2H2O

Applications of Noble Gases 1. Helium is used in weather balloons, in welding & in traffic

signal lights. 2. It is used as mixture (80% He & 20% O2) for sea divers as

nitrogen diffuses in to blood at high pressure. 3. Helium is also used as coolant for nuclear reactors 4. Neon is used in making neon advertising signs, high voltage

indicators & in TV tubes. 5. Neon & helium arc is used for making glass lasers.

Applications of Noble Gases

6. Argon is used in electric light bulbs, in fluorescent tubes in radio tubes and in Geiger Muller Counter (radioactivity detection).

7. Argon is used for arc welding and cutting.

8. Krypton is used to fill fluorescent tubes and in flash lamps for high speed photography.

9. Xenon is used in bactericidal lamps.

10. Radon being radioactive is used in radiotherapy for cancer and for earth quake prediction.


Documents

Introduction Occurrence Peculiar Behavior of Fluorine and ... · are good oxidizing agents. Usually they react with metals and oxidize them hence reducing themselves. 2Na + Cl 2 Æ