(i) In CIF₃, central atom CI has three bond pairs and two lone pairs.
(ii) According to VSEPR theory, the two lone pairs will occupy. The equatorial positions to minimise Ip-Ip and repulsions.
(iii) In addition, the axial fluorine atoms will be bent towards the equatorial fluorine in order to minimise the Ip-Ip repulsions.
(iv) Therefore CIF₃ has a bent T-shaped structure

(i) CI has vacant d-orbitals and hence can show an oxidation state of +3 but F has no d-orbitals, therefore, it cannot show positive oxidation states. Further, since F can show only - 1 oxidation state therefore it forms only CIF of FCI₃.
(ii) Due to larger size CI an accommodate three small F-atoms around it while F being smaller cannot accommodate three bigger sized CI atoms around it.

(i) All these acids on losing a proton give their corresponding conjugate bases (ie) ClO-,
CIO₂ ^-, CIO₃ - and CIO₄ ^-. Their structures are:

(ii) Since, oxygen is more electronegative than chlorine, therefore dispersal of negative charge present on oxygen atom (Singly bonded to CI) increases as the number of oxygen atoms attached by a double bond: to chlorine increases due to \(P\pi -d\pi \) back bonding.
(iii) Therefore stability of ions will increase in the following order:
CIO- < CIO₂- < CIO₃- < CIO₄-
(iv) Due to increase in stability of conjugate bases, acidic strength of corresponding acid increases in the same order as :
HCIO- < HCIO₂ < HCIO₃ < HCIO₄

(i) Bond angel of HiX (H-O-H=104.5^o) is larger than that of H₂S(H-S-H=92^o)
(ii) Since oxygen is more electronegative than sulphur, therefore bond pair electrons of O-H bond will be closer to oxygen which will be little away from the sulphur atom.
(iii) As a result bond pair-bond pair repulsions between bond pairs of two O-H bonds would be stronger than in the S-H bonds.

(i) The thermal stability of hydrides of group 16 elements is directly proportional to the bond dissociation enthalpy of H- E bond.
(ii) On moving down the group, bond dissociation energy decreases and hence, E- H bond breaks easily.
(iii) Thus, the thermal stability of hydrides of group 16 elements decreases down the group. Hence the order of thermal stability is,
H₂O > H₂S > H₂Se > H₂Te > H₂Po

(i) Fluorine is the most reactive element among halogens due to minimum value of F- F bond dissociation energy.
(ii) It can form two types of salts with metals NaF and NaHF₂
(iii) AgF is soluble in water but other AgX are insoluble.
(iv) HF attacks glass while others do not.
(v) Fluorine, does not form any polyhalides (absence of d - orbitals)
(vi) Fluorine exhibit only negative oxidation state (highly electronegative) while other halogens have both +ve and -ve oxidation state.

(i) All halogens react with hydrogen to form volatile covalent hydrides of formula HX.
(ii) These hydrides are called hydracids.
(iii) Hydracids are the reducing agents.
(iv) Except HF, all hydrogen halides are gases. HF is a liquid because of intermolecular hydrogen bonding.
H-F...H-F....H-F....H-F
(v) The acidic character of HX are in the following order.
HF < HCI < HBr < HI.

(i) The element of group number 17 and period number 2 is fluorine (A).
(ii) The element of group number 17 and period number 4 is bromine (B).
(iii) (A) and (B) react to give an interhalogen compound (C) bromine pentafluoride
\(\underset { (A) }{ { Br }_{ 3 } } +\underset { (B) }{ { 5F }_{ 2 } } \longrightarrow \underset { (C) }{ { 2BrF }_{ 5 } } \)
(C) undergoes sp³d² hybridisation and has octahedral structure

(i) Both fluorine and oxygen have very high electron affinities and can easily cause the excitation of the electrons from 5p orbital to 5d orbital of xenon.
(ii) The unpaired electrons thus formed can take up electrons from oxygen or fluorine to form compounds.
(iii) Thus xenon has low ionisation energy and it can form compounds with strong oxidising agents (high E.A) like F₂ and O₂·

(i) Dilute solution of sulphuric acid/aqueous : solution of sulphates gives white precipitate (barium sulphate) with barium chloride solution.
(ii) It can also be detected using lead acetate solution. Here a white precipitate of lead sulphate is obtained
(iii) \({ BaCl }_{ 2 }+{ H }_{ 2 }{ SO }_{ 4 }\longrightarrow { { BaSO }_{ 4 } } \downarrow +2Hcl\)
                                   Barium sulphate (White precipitate)
(iv) \(\left( { CH }_{ 3 }COO \right) _{ 2 }Pb+{ H }_{ 2 }{ SO }_{ 4 }\longrightarrow { PbSO_4 }\downarrow +{ 2CH }_{ 3 }COOH\)
                                                     Lead Sulphate (White precipitate)

O₃ oxidises potassium iodide to iodine. This reaction is quantitative and can be used for estimation of ozone 
\({ O }_{ 3 }+2KI+{ H }_{ 2 }O\longrightarrow 2KOH+{ O }_{ 2 }+{ I }_{ 2 }\)

Commercial method of preparation
(i) Nitric acid prepared in large scales using Ostwald's process. In this method ammonia from Haber's process is mixed about 10 times, of air.
(ii) This mixture is preheated and passed into the catalyst chamber where they come in contact with platinum gauze.
(iii) The temperature rises to about 1275 K and the metallic gauze brings about the rapid catalytic oxidation of ammonia resulting in the formation of NO, which then oxidised to nitrogen dioxide.
\({ 4NH }_{ 3 }+{ 5O }_{ 2 }\longrightarrow 4NO+6{ H }_{ 2 }O+120KJ\)
\(2NO+{ O }_{ 2 }\longrightarrow { 2NO }_{ 2 }\)
(iv) The nitrogen dioxide produced is passed through a series of adsorption towers. It reacts with water to give nitric acid. Nitric acid formed is bleached by blowing air.
\({ 6NO }_{ 2 }+3{ H }_{ 2 }O\longrightarrow { 4HNO }_{ 3 }+2NO+{ H }_{ 2 }O\)

Structure of ammonia
(i) Ammonia molecule is pyramidal in shape N-H bond distance is 1.016Å and H-H bond, distance is 1.645Å with a bond angle 107°.

(ii) The structure of ammonia may be regarded as a tetrahedral with one lone pair of electrons in one tetrahedral position hence it has a pyramidal shape.

(i) Ammonia reacts with chlorine and chlorides to give ammonium chloride as a final product.
(ii) The reactions are different under different conditions as given below.
(iii) With excess ammonia
\({ 2NH }_{ 3 }+3{ Cl }_{ 2 }\longrightarrow { N }_{ 2 }+6HCl\)
\(6HCl+6{ NH }_{ 3 }\longrightarrow { 6NH }_{ 4 }Cl\)
(iv) With excess of chlorine ammonia reacts to give nitrogen trichloride, an explosive substance.
\({ 2NH }_{ 3 }+{ 6Cl }_{ 2 }\longrightarrow { 2NCl }_{ 3 }+6HCl\)
\({ 2NH }_{ 3 }(g)+{ HCl }{ (g) }\longrightarrow NH_4Cl(s)\)

Direct reaction of nitrogen with hydrogen gives ammonia. This reaction is favored by high pressures and at optimum temperature in presence of iron catalyst.
\(\cfrac { 1 }{ 2 } { N }_{ 2 }+\cfrac { 3 }{ 2 } { H }_{ 2 }\rightleftharpoons { 2NH }_{ 3 }\)\(\Delta H_f { }_{ }=-46.2KJmol^{ -1 }\)