(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) 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) 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)

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.
\({ 6NO }_{ 2 }+3{ H }_{ 2 }O\longrightarrow { 4HNO }_{ 3 }+2NO+{ H }_{ 2 }O\)

(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.
\({ 2NH }_{ 3 }+{ 6Cl }_{ 2 }\longrightarrow { 2NCl }_{ 3 }+6HCl\)
\({ 2NH }_{ 3 }(g)+{ HCl }{ (g) }\longrightarrow NH_4Cl(s)\)