Nitrogen Family

The p-Block Elements Nitrogen Family ELECTRONIC CONFIGURATION : CHEMICAL PROPERTIES : The general outer electronic configuration of elements 1. of VA group is ns2np3. Hence these elements belong to p-block. Hydrides : Elements Configuration NH3 Nitrogen [N7] [He] 2s22p3 Ammonia Phosphine Arsine Stibine Bismuthine Phosphorus [P15] [Ne] 3s2 3p2 Arsenic [As33] [Ar] 3d10 4s2 4p3 Antimony [Sb51] Bismuth [Bi83] 5s2 * [Kr] 4d10 [Xe] 4f145d106s26p3 N and P are non metals. * As and Sb are metalloids. Bi is of -course metal. * Nitrogen constitutes about 78% by volume of the atmosphere (essential constituent of fertilizers, explosives and proteins) PH3 AsH3 SbH3 BiH3 Hydrides are formed by the action of water of dilute acids on compounds : Mg3N2, Ca3P2, Zn3As2, 5p3 * MH3 type of hydride is formed : Mg3Sb2 and Mg3Bi2. * All hydrides are coloured gases. * NH3 is highly soluble other hydrides are less soluble. * Poisonous nature increases from NH3 to BiH3 Ammonia -----------------------------Bismuthine Basic character decreases   * Phosphorus occurs in bones, phosphate rocks. It is used as fertilizers. * As, Sb, Bi occur mostly as sulphides. Reducing nature increases   * Bi is the end product of (4n + 1) radioactive series. Dipole moment decreases   * Elements of this group are called pnicogens. Bond angle decreases   Thermal stability decreases   2. Oxides : Elements of VA group form oxides of the type M2O3, The p-Block Elements ANOMALOUS BEHAVIOUR OF NITROGEN : M2O4 and M2O5. Moving from : acidic nature of oxide decreases R L    Moving from acidic nature of oxide increases B T   3. Halides : Trihalides MX3 and penta halides * * * * NITROGEN DIFFERS FROM OTHER ELEMENTS OF ITS OWN GROUP : MX 5 * Nitrogen does not form pentahalides due to absence * of d-orbital. Trihalide (MX3) : All trihalides are stable except NCl3, NBr3 and NI3. The reason assigned to unstable nature of NCl 3, NBr3, NI3 is : (i) Low polarity of N–X bond * * * * (ii) Large difference in the size of nitrogen and halogen atom. Penta - Halides (MX5) : * PCl5, AsCl5 and SbCl5 are well known * Bi does not form penta halide due to inert pair effect. * The hybridized state of the central atom in liquid and * X-ray analysis have shown that PCl5 and PBr5 exist as ionic compounds [PCl4]+ [PCl6]– and [PBr4]+ Br–. * PCl5 undergoes thermal decomposition and also hydrolysed by water PCl5  PCl3 + Cl2 PCl5 + H2O  POCl3 + 2HCl POCl3 + 3H2O  H3PO4 + 3HCl * PCl5 acts as an effective chlorinating agent. Nitrogen is a gas while other elements are solids Nitrogen is diatomic, while other elements are tetratomic [P4, As4, Sb4] Nitrogen can form N3– ion (due to small size and high E.N.) Nitrogen is chemically inert under ordinary condition due to high dissociation energy of NN bond. Nitrogen shows oxidation state from –3 to +5 Hydride of nitrogen i.e. ammonia is stable and forms H-bonding. NITROGEN : * * * gaseous state is sp3 d showing trigonal bipyramidal geometry. The anomalous behaviour of nitrogen is due to : Small size High E.N. and high I.E. Non availability of vacant d-orbital Tendency to form multiple bond. 1. Nitrogen was discovered by Daniel Rutherford. It occurs in the atmosphere to the extent of 78% by volume. Nitrogen occurs in the combined form in various compounds KNO3. NaNO3, NH4Cl, (NH4)2 SO4 etc. Preparation (a) From ammonia and its compounds  (i) 3 CuO + 2NH3   N2+ 3Cu + 3H2O (ii) CaOCl2 + 2NH3  3CaCl2 + 3H2O + N2 (bleaching powder) (iii) 2NH3 + 3Cl2  6HCl + N2 (iv) Laboratory method :  (1) NH4NO2(aq)   N2(g) + 2H2O (1) (2) (NH4)2Cr2O7  N2 + 2H2O + Cr2O3 (b) From air : Nitrogen is prepared commercially from air by liquefaction and fractional distillation . 2. Properties : 3. Physical The p-Block Elements Dinitrogen trioxide (N2O3), O.S. (+3), blue liquid (<253K) * It is colourless, tasteless and odourless gas * It is highly soluble in water * Its m.p. is 63.2 K and b.p. is 77.2 K * It is absorbed by charcoal Chemical : Few reactions of N2 are * 253K NO(g) + NO2(g)   N2O3(g) 4. Nitrogen dioxide (NO2), O.S. (+4) brown gas. 5. Dinitrogen pentoxide (N 2 O 5 ), O.S. (+5), colourless gas (i) Li, Mg, Ca, Al form nitrides  3Ca + N2   Ca3N2 (ii) N2 + O2  2NO (electric arc) Preparation : OXY-ACIDS OF NITROGEN : This reaction forms the basis for the manufacture Nitrous acid [HNO2] of HNO3 by Birk land and Eyde process. * Preparation : (iii) CaC2 + N2 1273K   CaCN2 + C calcium carbide 3. * N2O3 + H2O  2HNO2 calcium cyanamide NaNO2 + HCl  NaCl + HNO2 Since CaCN2 gives ammonia when reacts with Properties water. Therefore [CaCN2 + C] called nitrolium and * It is a weak acid and does not exist in free liquid it is used as fertilizer. state. In aqueous solution it is unstable and changes Uses : to HNO3. Used for the manufacture of NH3, HNO3, CaCN2 etc. * To provide inert atmosphere N2 gas is used in metallurgical processes. * It is used in filling electric bulbs. 3HNO2  HNO3 + H2O + 2NO * It acts both as an oxidizing as well as reducing agent. * Oxidizing properties : 2HNO2  2NO + H2O + [O] OXIDES OF NITROGEN : H2S + [O]  H2O + S 1. 2KI + H2S + [O]  2KOH + I2 * Nitrous oxides [N2O], O.S. (+1), laughing gas, colourless. Preparation :  NH4NO3  N2O + 2H2O 2FeSO4 + H2SO4 + [O]  Fe2(SO4)3 + H2O * HNO2 + [O]  HNO3 Resonance :  ..  : N  N – O.. :  : N .. = N = Br2 + H2O + HNO2  HNO3 + 2HBr  O: * Special features : Oxide is neutral * It acts as an anaesthetic agent. 2. Nitric Oxide [NO], O.S. (+2) colourless gas. * Preparation Reducing properties : H2O2 + HNO2  HNO3 + H2O HNO KMnO4   MnSO4 2 * HNO Organic reactions : Urea   N2 2 HNO Ethyl amine   ethyl alcohol 2 1100K, Pt 4NH3 + 5O2   4NO + 6H2O HNO Aniline   diazonium chloride 2 The p-Block Elements Other Reaction : AMMONIA [NH3] 1. (vii) 2Na + 2NH3  2NaNH2 + H2 Preparation Laboratory method : 2NH4Cl + Ca(OH)2  CaCl2 + 2NH4 + 2H2O Mg3N2 + 6H2O  3Mg(OH)2 + 2NH3 (viii) 4NH3 + 3O2  2N2 + 6H2O (ix) K2HgI4 + NH3 + 3KOH  NH3 – HgO.HgI + 7KI + 2H2O (red brown ppt.) (x) The gas is collected by downward displacement of air. 3. * The gas is dried by CaO [P2O5, H2SO4 and CaCl2 * react with ammonia] * Manufactures : * Haber Process : * Fe, Mo  2NH N2 + 3H2  * 450ºC,250atm 3 * Cyanamide process : * FeCl3 + 3NH3 + 3H2O  Fe(OH)3 + 3NH4Cl (brown ppt.) Uses : Due to lone pair of electrons it acts as a lewis base. Preparation of fertilizers. In making artificial silk. As a laboratory reagent. In refrigeration. In making HNO3, (NH4)2CO3, Na2CO3 etc. o 1000 C CaC2 + N2   CaCN2 + C CaCN2 + 3H2O  CaCO3 + 2NH3 PHOSPHORUS : Occurrence : Five important minerals of phosphorus are : Serpeck’s process : Al2O3 + 3C + N2  2AlN + 3CO AlN + 3H2O  Al (OH)3 + NH3 2. Properties : Physical * Lighter than air * Easily liquefied by cooling or compression * Highly soluble in water. The solution is alkaline * Forms H–bonding with water. * Turns litmus to blue [NH3 + H2O  NH4+ + OH–] * Phosphorite Ca3(PO4)2 * Fluoropatite 3Ca3(PO4)2.CaF2 * Hydroxyapatite 3Ca3(PO4)2.Ca(OH)2. * Chloroapatite 3Ca3(PO4)2.CaCl2 It is mainly present in bones and teeth which constituent about 58% calcium phosphate and also in animal cells (DNA). Isolation : It is isolated by heating Ca3(PO4)2 with coke and silica in an electric furnace. (i) NH3 + HCl  NH4Cl 1770 K 2Ca 3 (PO 4 ) 2 + 6SiO 2  6CaSiO 3 + P 4O10 (ii) 2NH3 + H2SO4  (NH4)2SO4 P4O10 + 10C  P4 + 10CO Chemical : Few of the chemical reaction are : (iii) 2NH3 + 3CuO  3Cu + 3H2O + N2 PHOSPHORUS PENTOXIDE [P4O10] (iv) CaCl2 + 8NH3  CaCl2.8NH3 (v) With Cl2 (a) 8NH3 + 3Cl2  N2 + 6NH4Cl (b) NH3 + 3Cl2  NCl3 + 3HCl (vi) Complex formation : 2NH3 4NH3 Ag +   [Ag(NH 3 ) 2 ] +, Cu +2   [Cu(NH3)4]2+ , It is formed by burning phosphorus in excess of air : P4 + 5O2  P4O10 Note : Since it is collected as snowy powder hence it is called The p-Block Elements Flower of phosphorus. Dissolution in cold water : P4O10 + 2H2O (cold)  4HPO3 metaphosphoric acid Dissolution in hot water : P4O10 + 6H2O  4H3PO4 orthosphosphoric acid Similarly : OXY-ACIDS OF PHOSPHORUS : There are two series of oxyacids of phosphorus. * Phosphorus acid series. * Phosphoric acid series. Three prefixes meta, pyro and hypo is used while naming the oxy acids of phosphorus. * –H2O 2 × phosphors acid   TYPICAL EXAMPLES : Meta is used for acid obtained by loss of H2O 1. molecule from one acid molecule. 2. HPO3 [metaphosphoric acid] Pyro is used for acid obtained by loss of H2O molecule form two acid molecules Give one reaction showing oxidising property of HNO3. Thermally most stable oxide of nitrogen is : NO 2 × orthophosphoric acid 5. Hypo is used for the acid having lower oxygen content than the parent acid. What is glacial phosphoric acid. H2S + 2HNO3  2H2O + 2NO2 + S 4. * NaH2PO4, Na2HPO4 and Na3PO4. Metaphosphoric acid HPO3 3. * Three series of salts of H3PO4 are Nature of oxides on moving from P to Bi P2O6 (acidic), As4O6 and Sb4O6 (amphoteric) Bi2O3 (basic)