Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) The p Block Elements – Introduction The right side of the periodic table having group number 13, 14, 15, 16, 17 and 18 are known as p – block elements. These elements have 3, 4, 5, 6, 7 and 8 electrons in their outer most shell, respectively. The last electron of these groups’ elements occupies the position in p – sub shell that is why are added as p – block elements. Their general configuration is ns2np1-6. Some important properties of p-block (1) Electron affinity Illustration 1. Electron affinity increase from left to right along the period amongst Which of the following arrangements represent the correct order of the p – block elements and it decreases from top to bottom. But electron affinity of the given atomic species? group 15 is having exceptionally low values of electron affinity and is (A) F < Cl < O < S (B) S < O < Cl < F due to extra stability because of the presence of exactly half filled (C) O < S < F < Cl (D) Cl < F < S < O orbital in their valence shell. Similarly, elements of group 18 (noble Solution: © gases) have zero affinities due to presence of complete octet which provides then stability. The elements of groups 15 are nitrogen (N), phosphorous (P), (2) Metallic Character arsenic (As), antimony (Sb) and bismuth (Bi). The first two elements The metallic character is governed by N and P are non – metal. The next two, arsenic and antimony are (i) Size of atoms and metalloids whereas the last element, bismuth is a metal. The general (ii) Ionization energy. electronic configuration of this group is ns2np3. The elements having bigger size and low ionization energy has a General Introduction to the nitrogen family members greater metallic character. After combining both above mentioned Nitrogen (N) factors we observe that the elements with above two properties are Nitrogen gets its name from a mineral known as “niter” (potassium located in left corner of p – block and strong non – metallic elements nitrate), from which it can be prepared. It was discovered by a are located at right corner and a diagonal strip of elements Scottish physician Daniel Rutherford in 1770. separates thus two, having in between properties are called as Nitrogen is a fairly common element in the earth’s crust. It is most metalloids. important constituent of atmosphere, making up to 78.08 %. The (3) Oxidation state greatest use of nitrogen is in ammonia which is used for fertilizer The p – block elements show variety of oxidation states both positive production and to produce nitric acid. Nitrogen gas is used where and negative. Some of the p – block elements show different inert atmosphere is needed, such as in an ordinary light bulb. oxidation state due to inert – pair effect, where their lower oxidation Nitrogen is also used in protecting historic documents. Nitrogen is state is more predominant. also used in storage of food stuff and in explosives. Some important characteristics of p – block in tabular form Nitrogen is absolutely essential to all living organisms. It is important part of all protein molecules which, among other functions, are the building materials in all kinds of cells. Nitrogen oxides (from combustion) are one of the cause of toxic rain.

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) Phosphorous (P) growth. Most infamous use of arsenic is a poison. Arsenic also used Phosphorous got its name because it glows in the dark. in semi conductor devices along with phosphorus. “Phosphorous” is from the greek word phos (light) and phoros Antimony (Sb) (bearer). It was first isolated in 1699 by German physician Henning The name antimony is derived from the Latin words “anti + monos” Brand. He discovered it from urine. which means “not alone”. The symbol for antimony comes from its It is a non – metals. As a gas it is colourless, but it occurs in 3 original Latin name stibium. It was studied by Nicholos Lemery in allotropic form in solid state. There are white (or yellow) 17th century. phosphorous, red phosphorous and black phosphorous. The most The standard state of antimony is solid at 298 K. It is very brittle common and reactive of which is white (or yellow) phosphorous and flakes easily. Antimony has a bluish – white metallic sheen. It is which looks like a waxy. Transparent solid with a garlic like odour. a poor conductor of heat and electricity. It is known to be severely Red phosphorous is much less reactive. It is red powder and does toxic. It causes damage to the liver and is used in some cases to not dissolve in most liquids. induce vomiting and sweating. Black phosphorous is produced by heating white phosphorous in the It is added to iron and iron alloys to increase its hardness, stiffness presence of a mercury catalyst and a seed crystal of black and reduce corrosion. Antimony sulphides are used in the phosphorous. It is least reactive, does not ignite easily. vulcanization of rubber as well as in pigments. Commercially, phosphorous compounds are used in the manufacture Bismuth (Bi) of phosphorus acid (H3PO4) which is found in soft drinks, used in It’s name came from the German word Wissmuth which means fertilizers. Also phosphorous is used in fireworks, phosphorescent “white mass”. Its symbol is Bi from Bismuth. It was distinguished compounds. Phosphorous is used in forming china clay. Also used in from tin and lead by Claude Geoffroy in 1753. glass making. Bismuth is the heaviest non – radioactive naturally occurring Arsenic (As) element. It is a hard, brittle metal with an unusually low melting It was first recognized as an element by alchemists. Although it is point (271°C). Bismuth is a white – silvery crystalline, brittle metal not certain where and when arsenic was actually discovered, credit with a pinkish tinge. It is rare metal usually arrociated with copper, for the discovery usually goes to alchemist Albert the great in 1250 lead, tin, silver and gold ores. AD. It unusual property to expand upon solidification makes it useful in Arsenic is occasionally found as a free element, but it is usually type – metal alloys and for coating. Bismuth is used in wide variety found in a number of minerals. Elemental arsenic occurs in two solid of pigments ranging form cosmetics to the coloration of glass. modifications: Yellow and grey or metallic. It is a steel gray, very Illustration 1. brittle, crystalline metalloid. Arsenic does not melt when heated but Why the first ionization energy of group 15 elements much higher changes directly in to a vapour (sublimation). Arsenic is stable in dry than those of corresponding group 14 elements? air, but the surface oxidizes slowly in moist air to give a bronze Solution: This is due to increase in nuclear charge and extra stable tarnish and finally a black covering to the element. When heated in configuration of the elements of this group. The extra stability of air, arsenic combines with oxygen to form arseneous oxide (As2O3). configuration is attributed to the exactly half filled p – orbitals in A blue flame is produced and the compounds give off distinctive their valence shells. garlic – like odour. Illustration 2. It is necessary ultra trace element for humans, red algae, chickens, Why the tendency of catenation is less in nitrogen as compared to rats, goats and pigs. A deficiency of arsenic results in inhibited carbon?

Ambikapatty, Silchar-4 9476699055 Page 3 Ambikapatty, Silchar-4 9476699055 Page 4 Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) Solution: The lesser tendency of nitrogen to catenate as compared Nitrogen has one special feature that it can form pπ – pπ multiple with carbon can be understood in terms of their bond energies, as bonds with itself, carbon and oxygen due to its small size. In listed below. phosphorus rather pπ – pπ, dπ – pπ is found as in POX3 1. Hydrides All elements of this group form gaseous hydrides of the type MH3. The stability however decreases down the group for these hydrides. As there is a big drop in the bond energy from carbon to nitrogen, NH3 PH3 AsH3 SbH3 BiH3 evidently the tendency of catenation decreases enormously. Ammonia Phosphine Arsine Stibine Bismuthine Illustration 3. All the hydrides are strong reducing agents and reacts with metal Which allotrope of phosphorous is used on top head of match stick? ions to give phosphides, arsenides or antimonides. Phosphine and Solution:Red Phosphorous. other hydrides of heavier members of this groups are highly GENERAL TRENDS IN PHYSICAL PROPERTIES poisonous.

Structure of Hydrides Illustration 1. Name three allotropes of phosphorous? Which of the three is most reactive? Solution: White or yellow, red and black. White phosphorus is most reactive. CHEMICAL PROPERTIES OF GROUP 15 As we move down the group there is a decrease in covalent character. N > P > As > Sb > Bi Nitrogen is chemically less reactive, due to high stability of its molecule, N2 in which two nitrogen atoms are combined through triple covalent bonds (N ≡ N) from which one is sigma (σ) and two are pie (π) bonds, thus posses high bond strength (941.4 KJ mol-1).

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada)

Nitrogen forms three different hydrides with hydrogen (i) NH3 (ii) Hydrazine, NH2NH2 (iii) Hydrazoic acid, N3H Ammonia (NH3) is one of the very important hydride found in traces in atmosphere. The atmospheric ammonia is formed by the bacterial decomposition of nitrogenous matter of plants and animals. It was isolated in 1774 by priestly by the action of ammonium chloride and lime.

It was named alkaline air. Berthelot, in 1788, pointed out that ammonia is a compound of nitrogen and hydrogen. IN 1800, Davy established its formula NH3. Preparations Manufacture of NH3 (i) Haber’s process

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Physical Properties (i) It is colourless gas with a characteristic pigment odour. (ii) It is highly soluble in water due to hydrogen bonding. The solubility of ammonia increases with increase of pressure and decrease with increase of temperature. Chemical Properties Ammonia It is highly unstable. It decomposes into nitrogen and hydrogen at red heat or when electric sparks and passed through it.

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) Uses of Ammonia 1. Liquid ammonia is used in refrigeration. 2. Aqueous NH3 is used in qualitative as well as qualitative analysis in laboratory. 3. In manufacture of nitric acid (ostwald’s process), sodium bicarbonate (solvey process) and ammonium compounds. Ammonium sulphate, ammonium calcium phosphate. Calcium ammonium nitrate, etc are used as fertilizers. Ammonium nitrate is used in certain explosive. 4. It is used as a clanging agent for removing greese. 5. Ammonia is also used in the manufacture of urea which is an excellent fertilizer of nitrogen. Structure

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Physical Properties (i) It is a colourless gas having unpleasant garlic – like odour or rotten fish odour. (ii) It is heavier than air and sparingly soluble in water. (iii) It liquefies at – 89 degree C and solidifies at – 134 degree C. (iv) It is poisonous in nature.

Chemical Properties (a) Decomposition

Structure of phosphine

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) Phosphine is a covalent molecule. It has pyramidal structure like ammonia.

Two types of halides are available for this group. One is MX3 and another is MX5 type. PCl5exists as molecule in gaseous state but in solid it exists as MX3: NCl3, PCl3, AsCl3, SbCl3 and BiCl3 [PCl4]+ [PCl6]– and is ionic in nature. PBr5, PI5 also exist in the ionic MX5: PCl5, AsCl5, SbCl5 form in solid state. Illustration 1. Are all the five bonds of PCl5 equivalent? Justify your (a) Tri halides answer. (i) All trihalides are covalent except BiF3 which is ionic. Solution: PCl5 has trigonal bipyramidal structure. It has three (ii) Like hydrides these trihalides have pyramidal structure and a equivalent equatorial and two equivalent axial P – Cl bonds. central atom is sp3 hybridized. However, due to greater bond pair – bond pair repulsions, the axial P (iii) These trihalides can be easily hydrolyses by water except NX3. – Cl bonds are longer and hence different from the three equatorial PCl3 + 3H2O → H3PO3 + 3HCl bonds. AsCl3 + H2O → As2O3 + 6HCl Illustration 2. Among the trihalides of nitrogen, which one is the SbCl3 + H2O → SbOCl + 2HCl least basic? BiCl3 + H2O → BiOCl + 2HCl (A) NF3 (B) NCl3 (iv) The trihalides of P, As and Sb acts as Lewis acids and combine (C) NBr3 (D) NI3 with Lewis bases. Solution: (A) PF3 + F2 → PF5 SbF3 + 2F– → [SbF5]2- The elements of group 15 combines with oxygen directly or indirectly (b) Penta halides to form different types of oxides. In this central atom attains sp3d hybridization and forms five Oxidation state N P As Sb Bi covalent bonds with five chlorine atoms. of central atom Penta halides have less thermal stability as compared to trihalides. 5 N2O5 P4O10 As2O5 Sb2O5 Bi2O5 All penta halides act as Lewis acids. PCl5 + Cl– → PCl6– 4 N2O4, NO2 P4O8 – – – SbCl3 Cl – → [SbCl4]– 3 N2O3 P4O6 As2O3 Sb2O3 Bi2O3 2 NO – – – – 1 N2O – – – –

Ambikapatty, Silchar-4 9476699055 Page 15 Ambikapatty, Silchar-4 9476699055 Page 16 Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) Nature of oxides All the oxides of nitrogen and phosphorus are strongly acidic in nature (except NO and N2O); oxides of arsenic are weakly acidic; oxides of antimony are amphoteric and oxides of bismuth are weakly basic. This can be explained on the basis of increase in size of central atom. In lower element oxides, atom has small size and it can more strongly pulls the electron pair between O-H bond in water and thus helps in release of H+ ions.

Formation of oxides 1. Formation of oxides of nitrogen

2. Formation of oxides of phosphorus

The oxides of As(III) and Sb (III) can also be prepared by heating these elements in air. 3. Structures of oxides

Illustration 1. The reddish brown coloured gas formed when nitric oxide is oxidized by air is (A) N2O5 (B) N2O4 (C) NO2 (D) N2O3 Solution: (C)

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) Illustration 2. Methods of preparation Which of the following oxides is the most acidic? (a) Laboratory preparation (A) N2O5 (B) P2O5 KNO3 + H2SO4 → KHSO4 + HNO3 (C) As2O5 (D) Sb2O5 (b) Birkeland Eyde process Solution: (A) N2 + O2 ⇌ 2NO – 43,200 calories Oxides of N, P and As when dissolves in water to form oxy acids. The formation of nitric oxide is favoured by high temperature thus it Oxy acids of Sb and Bi are not stable. is maintained at 3000°C. Some important oxy acids: The nitric oxide is cooled to 1000oC as to prevent its decomposition. Formula of Name of Oxidation state of Element Nitric oxide further combines with O2 . the oxyacid the oxyacid element in oxyacid 2NO + O2 → 2NO2 Hyponitrous The vapours then passed through water when nitric acid is produced. Nitrogen H2N2O2 1 acid 2NO2 + H2O → HNO3 + HNO2 HNO2 Nitrous acid 3 3HNO2 → HNO3 + 2NO + H2O (c) Ostwald’s process (Modern process) HNO3 Nitric acid 5 In this process the nitric acid is formed first when NH3 and air Hypo Phosphor passed over platinum gauze at 750 – 900°C H3PO2 phosphorus 1 us acid Phosphorus H3PO3 3 The nitric oxide is then oxidised to NO2 by air which is cooled to acid 50°C and absorbed in water. Phosphoric H3PO4 5 2NO + O2 → 2NO2 acid 3NO2 + H2O → 2HNO3 + NO Metaphosph Fuming nitric acid (HPO4)n 5 oric acid When NO2 is dissolved in conc. nitric acid it forms fuming nitric acid. Pyrophospho It is brown in colour. It is obtained by distilling concentrated HNO3 H4P2O7 5 ric acid with a little starch. Physical properties Arsenious Arsenic H3AsO3 3 HNO3 is colourless fuming with pungent smell soluble in water. Nitric acid acid usually acquires yellow H3AsO4 Arsenic acid 5 colour due to its decomposition by sunlight into NO2 . Sb & Bi No stable acid

Oxyacids of Nitrogen , HNO3 , Nitric acid Chemical properties Nitric acid is also known as aqua fortis (meaning strong water) which was given by alchemists.

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Oxyacids of phosphorus Phosphorus forms two series of oxyacids namely; phosphorus acid and phosphoric acid.

(a) Phosphorus acid series The series consists of p atom exhibiting oxidation state of +3. They act as reducing agents.

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada)

Special Note (i) Meta is used for acid obtained by loss of H2O molecule. (ii) Pyro is used for the acid obtained from two molecules with a loss of H2O. (iii) Hypo is used for the acid having lower oxygen content than the parent acid. Phosphorus acid (H3PO3 ) Preparation and Properties

(b) Phosphoric acid series This series consist of acids having P in +5 oxidation state.

Ambikapatty, Silchar-4 9476699055 Page 23 Ambikapatty, Silchar-4 9476699055 Page 24 Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) (a) It is a transparent deliquescent crystalline solid. It melts at 42.3°C. It absorbs water and forms colourless syrupy mass. It is highly soluble in water.

Meta phosphoric does not exist in monomeric form, but it exists as cyclometa phosphoric acid (HPO3)3 or polymeta phosphoric acid (HPO3)n. Orthophosphoric acid (H3PO4 ) This acid is commonly called as phosphoric acid. Preparation (i) P4O10 + 6H2O → 4H3PO4 (ii) PCl + 4H2O → H3PO4 + 5HCl (iii) Laboratory preparation P + 5HNO3 → H3PO4 + H2O + 5NO2 This reaction is carried out in the presence of a crystal of iodine. Iodine acts as a catalyst. (iv) Industrial preparation It is prepared from bone ash. Illustration 1. Name the three series of salts formed when ⇒Ca3(PO4)2 + 3 H2SO4 → 3CaSO4 + 2 H3PO4 orthophosphoric acid reacts with sodium hydroxide. Solution: NaH2PO4, Na2HPO4 and Na3PO4. When bone ash is dissolved in HNO3 and lead acetate it forms Illustration 2. Which of the following is a cyclic oxo acid? Pb3(PO4)2 (A)H4P2O7 (B) H4P2O6 Pb3(PO4)2 + 3H2S → 3PbS + 2H3PO4 Properties (C) H3P3O9 (D) H5P5O15

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada)

Solution: (C) Illustration 3. Which of the following species is basic and reducing? (A) SO32- (B) SO42- (C) S2O42- (D) HSO42- Solution: (A)

FERTILIZERS For the proper development and natural growth of plants they require adequate supply of essential nutrients. Nitrogen, phosphorus and potassium are regarded as essential plant nutrients and are consumed in large quantities. To overcome the deficiency of these nutrients in soil additional materials containing N, P and K are added to it in the form of manures. Manures are of two types (i) Natural and (ii) Artificial Artificial fertilizers are the chemical substances which are added to the soil as to make up the deficiency of essential elements are called fertilizers.

Nitrogenous fertilizers The important nitrogenous compounds used as fertilizers are :

(v) Urea, NH2CONH2 Preparation CO2 + 2NH3 → NH2COONH4 (Ammonium carbonate) NH2COONH4 → NH2CONH2 + H2O Out of all, urea is having highest nitrogen content (46.6%). It does not even alter the pH of soil. It can be used for all type of crops. Phosphatic fertilizers

Ambikapatty, Silchar-4 9476699055 Page 27 Ambikapatty, Silchar-4 9476699055 Page 28 Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) Its name came from oxys + genes, “acid former” was discovered in 1772 by Schelle and independently by Pristeley in 1774. Oxygen is the most common element in the earth’s crust and makes up about 20% of the air we breathe. Oxygen is gas at room temperature and is colourless, odourless and testless. Liquid oxygen has a slight blue colour. Oxygen exists in two allotropes, oxygen in air (O2) and ozone in air (O3) ozone is very reactive and used bleaching and disinfectant reagent. Sulfur Sulfur was classified as an element in 1777 by Lavoisier. Pure sulfur is testless and odourless with white yellow colour. Sulfur is the tenth most abundant element in the known universe. Sulfur exists in three allotropic forms. Two are crystalline and one is amorphous. The most significant compound of sulfur used in modern industrialized societies is sulphuric acid (H2SO4). Sulphur dioxide (SO2) is used in bleaching and refrigeration. SO2 gas reacts with water vapour in air to produce a weak acid, sulfurous acid (H2SO3) which contributes to the acid rain problem. Selenium It was discovered by Berzelius in 1818. Its name came from the Greek work Selene which is used for moon. It is an important semiconductor which is particularly sensitive to light. There are at NPK fertilizers lest two other allotropes of the element, including a semi – metallic Fertilizers containing N, P and K in suitable adjusted proportions are state. known as NPK fertilizers. These are obtained by mixing nitrogenous, Tellurium (Te) phosphatic and potash fertilizers in suitable proportion. Discovered by Von Reicherstein in 1782. It is brittle metalloid that is relatively rare. It is named from the Latin tellus for ‘earth’. Tellurium Oxygen family can be alloyed with same metals to increase their machinability and is a basic ingredient in the manufacture of blasting caps. Group 16 of periodic table includes oxygen (O), Sulphur (S), Polonium (Po) Selenium (Se), Tellurium (Te) and Polonium (Po). These are It was discovered in 1898 by Marie Curie and named for her native collectively known as Chalcogens or ore forming elements. The first country Poland. Although radioactive, polonium has a few four members are non – metals. Polonium is having metallic commercial uses. It is synthesized in the lab rather its recovery from character and is radioactive. minerals. General introduction to Oxygen family GENERAL TRENDS IN PHYSICAL PROPERTIES

Oxygen

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) Seleniu Telluriu Poloniu Property Oxygen Sulfur m m m [He]2s2 [Ne]3s2 [Ar]4s2 [Kr]5s2 [Xe]6s2 Configuration 2p4 3p4 4p4 5p4 6p4 Common -2, +4, Radioacti oxidation -2 +4, +6 +4, +6 +6 ve state Atomic radius 66 104 116 143 167 (pm) First ionization 1314 1000 941 869 812 energy (KJ/ mol) Electronegati 3.5 2.5 2.4 2.1 2.0 vity Illustration 1. Name two compounds in which oxygen has oxidation state different from – 2. Give oxidation states also. Solution: (i) OF2 (Oxidation state of O = +2) (ii) H2O2 (Oxidation state of O = – 1)

CHEMICAL PROPERTIES OF GROUP 16 The group 16 elements show a lot of variation in their chemical behaviours. Both O and S are reactive but reactivity decreases down the group and oxygen reacts with almost all the elements. 1. Hydrides

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) OZONE O3 = Ozone was first observed through a rotten smell by Van Marum in 1758 which was confirmed by Schonbiln in 1840. Sorret established its formula O3, , and pointed out that the ozone is an allotrope of oxygen. Ozone prevents the living world from the harmful radiations (UV) coming from sun. Its layer lies 12 to 15 miles above earth’s surface. Near earth’s surface it is decomposed by dust particles.

Preparation of ozone Ozone is prepared in laboratory by passing silent electric discharge through dry oxygen. By passing the electric current some of the oxygen molecules dissociate and then atomic oxygen combines with oxygen molecules to form ozone.

The mixture thus obtained contains 5 – 10% ozone by volume and the mixture is called as ozonised oxygen. The apparatus used for this purpose is known as ozoniser. Recovery of pure ozone from ozonised oxygen The ozonised oxygen is passed through a spiral cooled by liquid air. Ozone condenses as its condensation temperature is 112.4°C. The liquid ozone thus obtained may contain some dissolved oxygen. This liquid is fractionally distilled to get pure ozone. Some other ozone forming reactions (i) Fluorine reacts with water at a very low temperature when mixture of ozonised oxygen is formed. 2F2 + 2H2O → 4HF + O2 2F2 + 3H2O → 6HF + O3 (ii) By action of ultraviolet rays, oxygen can be converted into ozone.

Ambikapatty, Silchar-4 9476699055 Page 35 Ambikapatty, Silchar-4 9476699055 Page 36 Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) (iii) The electrolysis of acidified water with high current density and platinum anode yields ozone on the anode. Nascent oxygen discharged at anode combines with molecular oxygen to form ozone. Physical properties (i) It is having characteristic rotten smell with pale blue colour. (ii) It can be liquefied into pale blue liquid at 112.4°C. If we reach at 249.7°C, it converts into violet black crystals. (iii) It is heavier than air. (iv) Solubility – It is slightly soluble in water but more soluble in turpentine oil, glacial acetic acid or carbon tetrachloride. (v) It causes headache and nausea when inhaled in small amount. Chemical properties

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) (vi) Moist iodine is oxidised to iodic acid (d) Formation of ozonides

Structure of ozone

Tests of ozone (i) It has a strong rotten smell. (ii) Metallic mercury loses its fluidity in contact with O3 . (iii) It turns an alcoholic solution of benzidine brown. (iv) It turns an alcoholic solution of tetramethyl base violet. (v) It turns starch – iodide paper blue. The important oxyacids of S, Se and Te are given in the table.

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But the oxyacids of sulphur are more important. Extraction of sulphur (a) Frasch Process In this method of extraction, sulphur is extracted from underground deposits. The underground deposits are melted through passing superheated (~ 440 K) steam down the beds of ore. The molten sulphur is then blown out with the help of compressed air.

(b) From natural gas Sulphur can be recovered from the natural gas which includes separating out of H2S by absorption into monoethanolamine and then converting H2S in to sulphur by the following sequence of reactions.

Allotropes of sulphur Main three types of allotropes of sulphur are discussed here: (a) Rhombic sulphur

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada)

Ambikapatty, Silchar-4 9476699055 Page 43 Ambikapatty, Silchar-4 9476699055 Page 44 Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) 5. Reaction with salts

Halogens

CHEMICAL PROPERTIES IN HALOGEN Among all the halogens fluorine is the most reactive and reactivity decreases down the group. The high reactivity of fluorine is due to high electronegativity and low bond dissociation energy among the group.

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada)

Ambikapatty, Silchar-4 9476699055 Page 47 Ambikapatty, Silchar-4 9476699055 Page 48 Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) The compounds of oxygen with fluorine are called as fluorides because fluorine is more electro negative than oxygen. Most of these compounds are endothermic and unstable and are likely to explode resulting in the formation of more stable products. All the oxides are powerful oxidizing agents and decompose explosively when they are given mechanical shock or heat. The structures of some molecules is as follows

5. Oxyacids

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) Inter halogen compounds

POLYHALIDE IONS

Ambikapatty, Silchar-4 9476699055 Page 51 Ambikapatty, Silchar-4 9476699055 Page 52 Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) Solution: (A)

Xenon and fluorine in the ratio 1:5 heated at 873 K at 7 bar pressure give xenon tetra fluoride.

Xenon and fluorine in the ratio 1:20 heated at 573 K at 60-70 bar pressure give xenon hexafluoride

Xenon hexafluoride can also be obtained by the reaction of xenon tetra fluoride and dioxygen difluoride at 143 K. 143 K XeF4 + O2F2 → XeF6 In 1962, Neil Bartlett predicted that xenon should react with platinum Xenon tetrafluoride Dioxygen difluoride Xenon hexafluoride hexafluoride He was the first to prepare a compound of xenon, called xenon hexafluoridoplatinate (V). Structural aspects of the fluorides of xenon: Later many compounds of xenon were synthesised, including fluorides, oxides Structure of XeF2: and oxy -fluorides. The central atom, xenon, in XeF2 undergoes sp3d hybridisation. Xenon di fluoride has 5 electron pairs. Of these, 3 are lone pairs and 2 are Methods to prepare xenon-fluorine compounds: bond pairs Xenon directly reacts with fluorine to form a binary fluoride, which may be The structure of xenon di fluoride is linear due to the presence of the 3 lone xenon di fluoride, xenon tetra fluoride or xenon hexafluoride. The product pairs of electrons on the central xenon atom. depends on the ratio in which xenon and fluorine reacts.

Xenon and fluorine in the ratio of 2:1 heated at 673 K at 1 bar pressure give xenon di fluoride

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) Properties of xenon fluorides: All the fluorides of xenon are white crystalline solids. They are strong oxidising and fluorinating agents. EX: Strong Oxidising Agents

XeF2 + 2HCl → Xe + 2HF + Cl2 Xenon Hydrochloric Xenon Hydrogen Chlorine difluoride acid Fluoride

XeF4 + 4HI → Xe + 4HF + 2I2 Xenon Hydroiodic Xenon Hydrogen Iodine Structure of XeF4: tetrafluoride acid Fluoride The central atom, xenon, in XeF4 undergoes sp3 d2 hybridisation. It has six electron pairs. Of these 4 are bond pairs and 2 are lone pairs. The structure of xenon di fluoride is square planar due to the presence of the 2 Fluorinating Agents lone pairs of electrons on the central xenon atom. XeF4 + 2PtF4 → Xe + 2PtF6 Xenon Platinum Xenon Platinum tetrafluoride tetrafluoride hexafluoride

XeF4 + 2SF4 → Xe + 2SF6 Xenon Sulphur Xenon Sulphur tetrafluoride tetrafluoride hexafluoride Structure of XeF6: Xenon tetrafluoride and xenon hexafluoride react violently with water, while The central atom, xenon, in XeF6 undergoes sp3 d2 hybridisation. xenon difluoride reacts slowly with water. It has 7 electron pairs. Of these 6 are bond pairs and 1 is a lone pair. Very Fast Reaction The structure of xenon hexafluoride is distorted octahedral owing to the 6XeF4 + 12H2O → 2XeO3 + 4 Xe + 24HF + 3O2 presence of the single lone pair of electrons on the central xenon atom. Xenon Water Xenon trioxide Xenon hydrofluoric acid tetrafluoride XeF6 + 3H2O → XeO3 + 6HF Xenon water Xenon Hydrofluoric hexafluoride trioxide acid Slow Reaction 2XeF2 + 2H2O → 2Xe + 4HF + O2 Xenon Water Xenon Hydrofluoric oxygen deifluoride acid

Ambikapatty, Silchar-4 9476699055 Page 55 Ambikapatty, Silchar-4 9476699055 Page 56 Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) Xenon fluorides form complexes called xenon fluoride complexes. (ii) Also used in beacon lights for safety of air navigators as the light They form complexes with covalent penta fluorides, such as phosphorus penta possesses fog and stram perpetrating power. fluoride, antimony penta fluoride and arsenic penta fluoride. (C) Argon Along with nitrogen it is used in gas filled electric lamps because argon is more inert than nitrogen.

Xenon difluoride reacts with phosphorus penta fluoride, while xenon tetra fluoride reacts with antimony penta fluoride. XeF2 + MF5 → XeF2.MF5 or [XeF]+[MF6]- Xenon Pentafluoride Xenon fluoride Cationic difluoride complex species XeF2 + PF5 → XeF2.PF5 or [XeF]+[PF6]- Xenon Phosphorus Xenon fluoride Cationic difluoride Pentafluoride complex species XeF2 + SbF5 → XeF2.PF5 or [XeF]+[SbF6]- Xenon Antimony Xenon fluoride Cationic difluoride Pentafluoride complex species

Uses of Nobles gas The noble gases are used in following ways: (A) Helium (i) It is used to fill airships and observation balloons. (ii) In the oxygen mixture of deep sea divers. (iii) In treatment of asthma. (iv) used in inflating aeroplane tyres. (v) Used to provide inert atmosphere in melting and welding of easily oxidizable metals. (B) Neon (i) It is used for filling discharge tubes, which have different characteristic colours and are used in advertising purposes.

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Topic: B.Tech, M.Tech Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada) Amlan Nag Univ.Of Alberta(Canada) Sol. Phosphorus forms PCl5 due to availability of vacant d – orbital though white P can extend its oxidation state but this is not applicable in case of N due to unavailability of d – orbitals.

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Topic: B.Tech, M.Tech Amlan Nag Univ.Of Alberta(Canada)

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