17th & 18th column

7/27/2019 17th & 18th Column

1/10

MarketedandDistributedbyFaaDoOEngineers.com

Nishant Gupta, D-122, Prashant vihar, Rohini, Delhi-85

Contact: 9953168795, 9268789880

17th & 18th COLUMN

GUPTA CLASSES

For any help contact:

9953168795, 9268789880

7/27/2019 17th & 18th Column

2/10



Contact: 9953168795, 9268789880

Halogens salt formers

17th column includes Fluorine, Chlorine, Bromine, Iodine and Astatine. All the members of the group are non-metals

Astatine is a radioactive element. Fluorine is most reactive halogen and is known as super halogen.

Occurrence

Halogens are highly reactive elements, so do not occur in Free State. They occur in combined state as halides.

FLUORINEIt occurs as insoluble fluorides

1. FluorsparCaF22. CryoliteNa3AlF63. Fluoroapatite3Ca3(PO4)2 . CaF2

Some amounts of fluorides are present in soil, river water, plants, bones and teeth.

CHLORINE

It is most abundant halogen.

1. Sodium chlorideRock saltNaCl2. CarnalliteKCl.MgCl2.6H2O3.

Calcium chlorideCaCl2.

BROMINE

In sea water and salt lakes as bromide of alkali metals and alkaline earth metals.

IODINE

1. In sea weeds as alkali metal iodides.2. Caliche containing iodine as sodium iodate (NaIO3)

1. Electronic configurationFluorine (F) At. No- 9 [He] 2s2, 2p5

Chlorine (Cl) 17 [Ne] 3s2, 3p5

Bromine (Br) 35 [Ar] 3d10, 4s2, 4p5

Iodine (I) 53 [Kr] 4d10, 5s2, 5p5

Astatine (At) 85 [Xe] 4f14, 5d10, 6s2, 6p5

2. Atomic and Ionic RadiiHave smallest atomic radii in the period. Atomic and ionic radii increase from top to bottom in the group due to addition

of one shell in each period.

3. Ionisation Enthalpy:Have very high I.E. which decreases from top to bottom due to increase in atomic radii.

4. Electron gain EnthalpyHalogens have highest value of negative electron gain enthalpy in their respective periods. Negative electron gain

enthalpy decreases from top to bottom. Fluorine has abnormally small value of electron gain enthalpy due to abnormally

small size. Order ofve electron gain enthalpy is Cl > F > Br > I.

5. Electro-negativityHalogens have highest electro negativity in the respective period. Electro negativity decreases from top to bottom in thegroup.

6. AtomicityAll halogens exist as diatomic molecules.

7. Melting point and Boiling pointAs molecular mass increases from top to bottom in the group so surface area increases from top to bottom in the group

so Vander Waals forces increase from top to bottom and b.pt. and m.pt. increase from top to bottom in the group. F

and Cl2 are gases at room temperature, Br2 is a liquid and I2 is a solid.

8. Enthalpy of dissociation

17TH

COLUMN ELEMENTS

7/27/2019 17th & 18th Column

3/10



Contact: 9953168795, 9268789880

Order of bond dissociation enthalpy is Cl2 > Br2 > F2 > I2. abnormally low value of bond dissociation enthalpy of F 2 is

due to very small size and large forces of repulsion between the lone pair of electrons.

9. ColourAll halogens are coloured due to absorption of light in the visible region. As energy required for excitation of electron

decreases from fluorine to iodine, so there is progressive deepening of colour from top to bottom. Fluorine is pale

yellow, chlorine is greenish yellow, bromine is orange red and iodine is deep violet.

10. SolubilityFluorine and chlorine react with water, bromine and iodine are sparingly soluble in water but are soluble in organic

solvents to give coloured solutions.

11. Oxidation statesHalogens have ns2, np5 electrons in valence shell, so they can gain one electron to acquire inert gas configuration, so

they show ve O.S. of -1. Tendency to show ve O.S. decreases from top to bottom. Fluorine being most

electronegative shows an O.S. of -1 only (does not show +ve O.S.). other halogens show +ve O.S. of +1, +3, +5 and +7

due to expension of valence shell. Higher O.S. of chlorine, bromine and iodine are shown in compounds with small and

highly electronegative fluorine and oxygen atoms. O.S. of +4 and +6 are shown in oxides and oxo-acids of chlorine and

bromine.

12. Oxidizing powerAs halogens have high tendency to accept electrons, so they act as strong oxidizing agent. As tendency to accept

electrons decreases from top to bottom in the group so oxidizing nature decreases from top to bottom in the group. A

halogen can oxidize halide ion of higher atomic number.F2 + 2X

2F+ X2 (X = Cl, Br, I)

Cl2 + 2X 2Cl+ X2 (X = Br, I)

Br2 + 2I 2Br+ I2

F2 oxidises water to oxygen2F2 (g) + 2 H2O (l) 4H

+ (aq) + 4F(aq) + O2 (g)

Cl2 and Br2 react with water to give hydrohalic and hypohalous acid.X2 + H2O HX +HXO (X = Cl or Br)

13. Anomalous behaviour of FluorineDue to small size, highest electronegativity, low FF bond dissociation energy and non -availability of nd-subshel

fluorine shows properties different from other members of the group. Most of reactions of fluorine are exothermic due

to small and strong bonds formed by it with other elements. It forms only one oxo acid whereas other halogens form

number of oxo acids. HF is a liquid due to intermolecular hydrogen bonding.

14. Reactivity towards hydrogenThey form hydrogen halides of the type HX. Fluorine forms H2F2 which is a dibasic acid, rest are monobasic acids.(i) Boiling points of hydrogen halides are in the order HF > HI > HBr > HCl.(ii) Bond dissociation energy are of the order HF > HCl > HBr > HI (iii) Acidic strength and reducing nature is of the order HI > HBr > HCl > HF(iv) HF dissolves silica and glass.

SiO2+ 4HF SiF4 + 2H2OSiF4+ 2HF H2SiF6 (Fluorosilicic acid) water soluble

15. Reactivity towards oxygenMost of the oxides of halogens are unstable. Fluorine forms OF2 and O2F2. Only OF2 is stable at 298K. Both oxides of

fluorine are strong fluorinating agents. O2F2 oxidises Pu to PuF6.Cl, Br, I forms oxides with O.S. from +1 to +7. Decreasing order of stability of oxide are I > Cl > Br. Higher oxides

tend to be more stable. Cl2O, ClO2, Cl2O6, Cl2O7 are highly reactive oxidizing agents and tend to explode. ClO2 is used

as a bleaching agent for paper pulp and textile. Br2O, BrO2, BrO3 are least stable. I2O4, I2O5 and I2O7 are insoluble oxidewhich decomposes on heating. I2O5 is a very good oxidizing agent and is used in the estimation of CO.

16. Reactivity with metalsMetal halides are obtained. Ionic character of metal halides is of the order MF > MCl > MBr > MI. Halides in higher

O.S. are more covalent than halides in lower O.S.

CHLORINE

Preparation

1. By heating conc. HCl with MnO2

7/27/2019 17th & 18th Column

4/10



Contact: 9953168795, 9268789880

MnO2 + 4HCl MnCl2 + 2H2O + Cl2

2. By heating NaCl and MnO2 with conc. H2SO44NaCl + MnO2 + 4H2SO4 MnCl2 + 4NaHSO4 + 2H2O + Cl2

3. By the action of KMnO4 on HCl2KMnO4+ 16HCl 2KCl + 2MnCl2 + 8H2O + 5Cl2

Manufacture

(i) Decons process: By oxidation of HCl gas by atmospheric oxygen in presence of CuCl2 (catalyst) at 723K.4HCl + O2

K723

2CuCl

2Cl2 + 2H2O

(ii) By electrolysis of brine solution, Cl2 gas is liberated at anode.Properties

Green yellow gas with pungent and suffocating smell, can be liquefied into greenish yellow liquid. Soluble in water.

Chemical properties

(i) React with number of elements to give chlorides2Al + 3Cl2 2AlCl3 2Na + Cl2 2NaCl

2Fe + 3Cl2 2FeCl3 P4 + 6Cl2 4PCl3

S8 + 4Cl2 4S2Cl2

(ii) Affinity with hydrogenH2 + Cl2 2HCl H2S + Cl2 2HCl + S

C10

H16

+ 8Cl2 16HCl + 10C

(iii) Reaction with NH3(a) Excess of NH3

8NH3 + 3Cl2 6NH4Cl + N2

(b) Excess of Cl2NH3 + 3Cl2 NCl3 + 3HCl

(iv) Reaction with cold and dilute NaOH2NaOH + Cl2 NaCl + NaClO + H2O

With hot and conc. NaOH

6NaOH + 3Cl2 5NaCl + NaClO3 + 3H2O

(v) With dry slaked limebleaching powder is obtained.2Ca(OH)2 + 2Cl2 Ca(OCl)2 + CaCl2 + 2H2O

Bleaching powder is a mixed salt having composition Ca(OCl)2.CaCl2.Ca(OH)2.2H2O

(vi) With hydrocarbons(a) Saturated hydrocarbons- substituted products are formed.

CH4 + Cl2 h

CH3Cl + HCl

(b) Unsaturated hydrocarbons-addition products are obtainedC2H4 + Cl2 C2H4Cl2

(vii) Chlorine dissolves in water to give HCl and HClO. HClO decomposes to give nascent oxygen which isresponsible for oxidizing and bleaching properties of chlorine.

(a) Oxidises Fe2+ to Fe3+, SO32to SO4

2, SO2 to H2SO4 and I2 to HIO32FeSO4 + H2SO4 + Cl2 Fe2(SO4)3 + 2HCl

Na2SO3 + Cl2 + H2O Na2SO4 + 2HCl

SO2 + 2H2O + Cl2 H2SO4 + 2HCl

I2 + 6H2O + 5Cl2 2HIO3 + 10HCl(b) It is a powerful bleaching agent due to oxidation

Cl2 + H2O 2HCl + O

Coloured substance + O Colourless substance

Uses

1. For bleaching wood pulp, cotton and textile2. In extraction of gold and Platinum3. In sterilizing water.4. In manufacture of dyes, drugs and organic compounds.5. In preparation of toxic gases like Phosgene, Tear gas and Mustard gas.

7/27/2019 17th & 18th Column

5/10



Contact: 9953168795, 9268789880

HYDROGEN CHLORIDE

Lab-Preparation

By heating NaCl with conc. H2SO4

NaCl + H2SO4 K420 NaHSO4 + HCl

NaHSO4 + NaCl K823 Na2SO4 + HCl

HCl gas is dried by passing through conc. H2SO4

Properties

Colourless, pungent smelling gas on cooling give colourless liquid. Highly soluble in water, ionizes as follows-

HCl (g) H2O (l) H3O+ (aq) + Cl(aq) Ka = 10

7. As value of K is very high so it is strong acid.

(i) It gives white fumes NH3NH3+ HCl NH4Cl

(ii) It decomposes salts of weaker acidsNa2CO3+ 2HCl 2NaCl + H2O + CO2

NaHCO3 + HCl NaCl + H2O + CO2

Na2SO3+ 2HCl 2NaCl + SO2 + 2H2O

Uses

1. In the manufacture of Cl2, NH4Cl etc.2. For extracting glue from bones3. As a lab. reagent

OXO-ACIDS OF HALOGENSDue to high electronegativity and small size fluorine forms only one oxo acid i.e. hypoflurous acid (HOF). All other

halogens also form halous acid (HOXO), halic acid (HOXO2) and perhalic acid (HOXO3).

Acidic strength of oxo-acids

HOCl > HOBr > HOIHOClO3 > HOClO2 > HOClO > HOCl

Oxi dizing power

HOCl > HOClO > HOClO2 > HOClO3

Structure

REACTIVITY TOWARDS HALOGENS INTER HALOGEN COMPOUNDSA halogen reacts with other halogens to form inter halogen compounds of type XX

', XX3

', XX5

'and XX7

'. X is larger

sized halogen and X'is smaller sized halogens.

ClF - (colourless gas), BrF(Pale brown gas), BrCl, ICl Ruby red solid. brown red solid. IBrblack solid.

ClF3colourless gas

Inter halogens compounds are covalent molecules diamagnetic in nature.

Preparation

Cl2 + F2 K437 2ClF Cl2 + 3F2 K573 2ClF3I2 +Cl2 2ICl Br2 + 3F2 2BrF3

I2 + 3Cl2 2ICl3 Br2 + 5F2 2BrF5

Properties

Inter halogens compounds are volatile liquids or solids. M.pt. and B.pt are little higher than corresponding halogens.

They are more reactive than halogens except fluorine due to weaker X X ' bond. All these undergo hydrolysis givinghalide ion derive from smaller halogen and hypohalite, halite, halate and perhalate ions derive from larger halogen.

ICl + H2O HCl + HIO

7/27/2019 17th & 18th Column

6/10



Contact: 9953168795, 9268789880

BrF5 + 3H2O 5HF + HBrO3

Inter halogen compounds may ionize as follows-

2ICl I+ + ICl2

2ICl3 ICl2+ + ICl4

Uses

1. Non-aqueous solvent2. Inter halogen compounds of fluorine are used as fluorinating agents

Structures

1. XX' linear structure2. XX3' sp3d-hybridisation, T-shaped structure.

3. XX5' sp3d2-hybridisation, square pyramidal.

4. XX7' sp3d3-hybridisation, Pentagonal bipyramidal.

Conceptual Questions1. Although electron gain enthalpy of fluorine is less negative as compared to chlorine, fluorine is a stronger oxidizing

agent than chlorine?

Ans- It is due to

(i) Low bond dissociation enthalpy of FF bond.(ii) High hydration enthalpy of F ions

2. Halogens have highest negative electron gain enthalpy in the respective period. Why?Ans- Halogens have smallest size in the period and therefore highest effective nuclear charge. So they readily

accept one electron to acquire noble gas configuration.

3. Give reason for bleaching action of Cl2.Ans- Cl2 reacts with water to give HCl and HOCl. HOCl decomposes to give nascent oxygen which oxidizescolouring substances to colourless substances.

4. Name two poisonous gases which can be prepared from chlorine.Ans- 1. Phosgene 2. Tear gas (Chloropicrin)

5. Give an equation of reaction of HCl with finely powdered iron.Ans- Fe + 2HCl FeCl2 + H2.

6. Why is ICl more reactive than I2?Ans-As ICl bond is weaker than II bond, so ICl is more reactive than I2.

7. Why are halogens strong oxidizing agent?Ans- Due to low bond dissociation enthalpy, high electro negativity and large negative electron gain enthalpyhalogens have a strong tendency to gain electrons.

X2+ 2e 2X

So halogens act as strong oxidizing agent. Oxidizing nature decreases from F2 to I2.8. Why fluorine forms only one oxo-acids?Ans- Due to small size and higher electronegativity fluorine forms only one oxo-acids i.e. HOF.

9. Why inspite of nearly same electronegativity oxygen forms H-bonding while chlorine does not?Ans-As Cl has large atomic size, so electron density per unit volume on Cl is much less than O. So O forms

H-bonds whereas Cl-does not.10. Write two uses of ClO2.

Ans- 1. As a powerful oxidizing agent and

2. As a bleaching agent.

7/27/2019 17th & 18th Column

7/10



Contact: 9953168795, 9268789880

11. Why halogens are coloured?Ans- Molecules of halogens absorb light in the visible region for the excitation of their electrons, remaining light is

transmitted. Colour of halogens actually is colour of transmitted light. As energy of excitation decreases from top to

bottom, so energy of transmitted light increases from top to bottom. So colour of halogens deepens from F2 to I2.

12. Write the reactions of F2 and Cl2 with water.Ans- 2F2 (g) + 2H2O (l) 4H

+ + 4F+ O2 (g)3F2 (g) + 3H2O (l) 6H

+ + 6F+ O3 (g)

Cl2 + H2O HCl + HClO

13. How can you prepare Cl2 from HCl and HCl from Cl2?Ans- HCl can be oxidized to Cl2 by oxidizing agents such as MnO2, KMnO4 etc.

MnO2+ 4HCl MnCl2 + 2H2O + Cl2

HCl is obtained by reaction of Cl2 with H2 in presence of diffused sunlight.

H2 + Cl2 l.s..d

2HCl

14. Write balanced equations for the following.(a) NaCl is heated with H2SO4 in presence of MnO2.

Ans- 4NaCl + MnO2 + 4H2SO4 MnCl2 + 4NaOHSO4 + Cl2 + 2H2O

(b) Chlorine gas is passed through solution of NaI in water.Ans- 2NaI + Cl2 2NaCl + I215. With what neutral molecule is ClOisoelectric?Ans- OF2

16. Arrange the following in order of property indicated for each set.(a) F2, Cl2, Br2, I2 Increasing bond dissociation enthalpy

Ans- I2< F2 < Br2 < Cl2

(b) HF, HCl, HBr,HI Order ofacid strength.Ans- HI > HBr >HCl > HF

17. Give the formula and describe the structure of following.(a) ICl4

, IBr2, BrO3

.

Ans-ICl4 :- There are four bond pairs of electron and two lone pair of electrons.

So I atom is sp3d2 hybridisation and has square plannar structure.

IBr2

:- It has two bond pair of electrons and three lone pairs of electron, it hasshow sp

3d hybridization. The two Br atoms are at axial position & it has linear shape

BrO3 :- Br atoms has three bond pairs of electron and one lone pairs of electron. So

it is sp3 hybridisation. It has a pyramidal shape.

7/27/2019 17th & 18th Column

8/10



Contact: 9953168795, 9268789880

18th

COLUMN ELEMENTS

Inert gases or Noble gasesGroup 18 includes Helium, Neon, Argon, Krypton, Xenon and Radon.

All of these are non-metals and gases at room temperature. As these gases are chemically unreactive, so they are known

as noble gases or inert gases. Radon is radio active.

Occurrence:

1. Noble gases except radon occur in air (about 1% volume of air) of which argon is major constituent.2. Natural gas contains 2-7% helium3. Radio active minerals : Helium and some times neon are found in minerals of radioactive origin. E.g. Pitch-

blende, monazite, clevite. Xenon and radon are rare. Radon is obtained as a decay product of Ra226

.

88Ra226 86Rn

222 + 2He4.

1. Electronic configuration

Element At. No. ConfigurationHelium (He) 2 1s2

Neon (Ne) 10 1s2, 2s2, 2p6

Argon (Ar) 18 1s2, 2s2, 2p6, 3s2, 3p6

Krypton (Kr) 36 1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s2, 4p6Xenon (Xe) 54 1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s2, 4p6, 4d10, 5s2, 5p6

Radon (Rn) 86 1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s2, 4p6, 4d10, 4f14, 5s2, 5p6, 5d10, 6s2, 6p6

2. Ionisation EnthalpyAs elements of 18th column have stable complete full electronic configuration, so they have very high I.E., highest in

the respective period. I.E. decreases from top to bottom due to increase in size from top to bottom.

3. Atomic RadiiThey have relatively larger atomic radii as their radii are Vander Waal radii. Atomic radii increase from top to bottomdue to addition of one shell in each period.

4. Electron gain enthalpyInert gases have stable electronic configuration, so they have no tendency to accept electron. So they have large +ve

value of electron gain enthalpy.

5. Physical PropertiesNoble gases are monoatomic, colourless, odour less and tasteless gases. They have very low b.pt. and m.pt. because of

weak inter atomic interactions (dispersion forces). B.pt. and M.pt. increase from top to bottom.

6. Chemical propertiesNoble gases are least reactive as

(i) Have completed full valence shell (ns2, np6).(ii) Have high I.E. & high +ve gain enthalpy.

Neil Bartlett observed thatI.E. of O2 and Xe were identical. When PtF6, which is a strong oxidizing agent was added to

O2 it oxidized O2 to a red compound O2+

[PtF6]

. He obtained Xe+

[PtF6]

by mixing PtF6 and Xenon. This was the first

compound of inert gases known.Only difluoride of Kr (KrF2) is studied. Compounds of Rn (RnF2) has been identified by radio tracer technique.No true

compounds of Ar, He and Ne are known. Several fluorides of Xenon are known.

XenonFl uori ne compounds

Xenon forms XeF2, XeF4 and XeF6.

Xe (g) + F2 (g) bar1,K673

XeF2 (s)

Xe (g) + 2F2 (g) bar7,K873

XeF4 (s)

1: 5 ratio

Xe (g) + 3F2 (g) bar7060,K573

XeF6 (s)

1:20 ratio

7/27/2019 17th & 18th Column

9/10



Contact: 9953168795, 9268789880

XeF4 + O2F2 K143

XeF6 + O2

XeF2, XeF4 and XeF6 are colourless solids, sublime at 298K. Powerful fluorinating agents. Readily hydrolysed by water.XeF2 (s) + 2H2O (l) 2Xe (g) + 4HF + O2

2XeF4 (s) + 3H2O (l) Xe + XeO3 + 6HF + F2

XeF6 + H2O XeOF4 + 2HF

XeOF4 + H2O XeO2F2 + 2HFXeO2F2 + H2O XeO3 + 2HF

Reaction with fluorides ion acceptorscationic species are formed.

XeF2 + PF5 [XeF]+ [PF6]

XeF4 + SbF5 [XeF3]+ [SbF6]

Reaction with fluoride ion donersanions are formed.

XeF6+ MF M+ [XeF7]

(M = Na, K, Rb or Cs)

XenonOxygen compounds

XeO3obtained by hydrolysis of XeF4 and XeF6.

6XeF4 + 12H2O 4Xe + 2XeO3 + 24HF + 3O2

XeF6 + 3H2O XeO3 + 6HF

XeO3 is a colourless explosive solid, XeOF4 is a colourless volatile liquid.

Structure of XeF2Xenon is sp3d hybridized. Both fluorine atoms at axial positions

(3 lone paor & two bond pair) linear shape

Structure of XeF4

Xe atom is sp3d2 hybridised. Two lone pairs and four bond pairs of electrons. square planar shape

Structure of XeF6Xe atom is sp3d3 hybridised. One lone pair,

six bond pairs of electrons. Distorted octahedral shape.

Structure of XeOF4

Xe atom is sp3d2 hybridised. One lone pair, five bond pairs of

electrons. square pyramidal shape

7/27/2019 17th & 18th Column

10/10



Contact: 9953168795, 9268789880

Structure of XeO3Xe atom is sp3 hybridised. One lone pair, three bond pairs of electrons.

Pyramidal shape

Uses1. He is used in filling balloons for meterological observations.2. He gas is used in gas cooled nuclear reactors.3. Liquid He is used as cryogenic agent.4. He is used to produce and sustain powerful super conducting magnets.5. Mixture of He and Oxygen is used for deep sea divers.6. Ne is used in discharge tubes and fluorescent bulbs. Ne bulbs are used in botanical gardens and green houses.7. Ar is used to provide inert atmosphere and filling electrical bulbs.8. Kr and Xe are used in filling incandescent metal filament bulbs.9. Rn is used in radio therapy of cancer.Conceptual Questions

1. Why are the elements of group 18 known as noble gases?Ans- Elements of 18th column have their valence shell complete full. They are unreactive and react with only few

elements under certain conditions, so they are known as noble gases.

2. Noble gases have very low boiling point. Why?Ans- Noble gases are monatomic gases and have very weak inter atomic interactions, so they have very low boiling

point.

3. Does the hydrolysis of XeF6 leads to a redox reaction?Ans- No, in this process O.S. of all the elements remains unchanged, so it is not a redox reaction.

4. Why is He used in diving apparatus?Ans- Due to low solubility of He in blood.

5. Balnce the following equationXeF6 + H2O XeO2F2 + HFAns - XeF6 + 2H2O XeO2F2 + 4HF

6. Why has it been difficult to study the chemistry of Rn?Ans- Rn is radioactive with very short half-life, so study of chemistry of Rn is difficult.

7. Which of the foolowing does not exist?(i) XeOF4 (ii) NeF2 (iii) XeF2 (iv) XeF6Ans- NeF2

8. Why noble gases have comparatively larger size?Ans- As their radii are Vander Waal radii.

17th & 18th column

Documents