Group 4 chemistry: key ideasElements in the second period of the periodic table have p orbitals ofthe same size as oxygen and so form strong pi bonds with oxygenSilicon in the third period has larger p orbitals which do not match insize and overlap well with oxygen's orbitals so strong pi bonds arenot formed.p orbitals of different sizep orbitals the same sizeproduce littleoverlapandproducegoodoverlapSweakbonds.andstrong元bonds.OO6
6 Group 4 chemistry: key ideas Elements in the second period of the periodic table have p orbitals of the same size as oxygen and so form strong pi bonds with oxygen. Silicon in the third period has larger p orbitals which do not match in size and overlap well with oxygen’s orbitals so strong pi bonds are not formed
Group 4 chemistry : key facts and ideasWordsWordsand ExpressionsCarbon; silicon; germanium; tin, leaddescendmetalloid: metalloidalcatenation: catenatehybridization; hybrid (hybrid orbitals); hybridizeoverlap7
7 Group 4 chemistry : key facts and ideas Words Carbon; silicon; germanium; tin, lead descend metalloid; metalloidal catenation; catenate hybridization; hybrid (hybrid orbitals); hybridize overlap Words and Expressions
Nitrogen chemistry: key factsNitrogen chemistry: key factsAMMONIAProperties due to the lone pair1. BaseNH,(g)+HCl(g) -NHCl(s) and NH,(g)+H,O(I)-NHt(aq)+OH(ag)2. Nucleophile2NH,(g) + CH,COCI(I) → CH,CONH2(s) +NH,Cl(s)3. Ligand4NH,(aq)+Cu2+(aq) → Cu(NH,)42+(aq)Redox propertiesNitrogen in ammonia has an oxidation state of-III and so can beoxidized to one of the many higher oxidation states of nitrogenAmmonia is therefore a reducing agent.8
8 Nitrogen chemistry: key facts Properties due to the lone pair 1. Base NH3 (g)+HCl(g) →NH4Cl(s) and NH3 (g)+H2O(l)→NH4 + (aq)+OH- (aq) 2. Nucleophile 2NH3 (g) + CH3COCl(l) → CH3CONH2 (s) +NH4Cl(s) 3. Ligand 4NH3 (aq)+Cu2+(aq) → Cu(NH3 ) 4 2+(aq) AMMONIA Redox properties Nitrogen in ammonia has an oxidation state of –III and so can be oxidized to one of the many higher oxidation states of nitrogen. Ammonia is therefore a reducing agent. Nitrogen chemistry: key facts
Nitrogen chemistry: key factsNITRICACIDAcidbasepropertiesNitric acid is a strong acidHNO,(I)+H,O(I) → H,O+(aq)+ NO,(aq) K, very largeRedox propertiesNitric acid contains nitrogen in the +V state and so it is readilyreduced. Nitric acid is therefore a strong oxidizing agent.9
9 Nitrogen chemistry: key facts Acid—base properties Nitric acid is a strong acid HNO3 (l)+H2O(l) → H3O+ (aq)+ NO3 - (aq) Ka very large NITRIC ACID Redox properties Nitric acid contains nitrogen in the +V state and so it is readily reduced. Nitric acid is therefore a strong oxidizing agent
Nitrogen chemistry: key facts*The manufacture of ammonia-theHaber processNitrogen and hydrogen are mixed in a l:3 mole ratio, heated,compressed, and passed over an iron catalyst. The reaction isexothermic, so the greatest equilibrium yield would be given by lowtemperature conditions. However, the rate is then too slow. At about500C20% of the reactants gases are converted to ammonia and theremainder recycled. It is important to remember that equilibrium isnever reached in the Haber process where new reactants areconstantly being added and ammonia is constantly being removedThe main uses of ammonia are for fertilizer production (80%),nylons, and nitric acid and explosivesN2(g)+3H(g) → 2NH,(g) △H= -92 kJ mol-1Temperature:500CPressure: between 200 and 1000 atmospheresCatalyst: Fe - a transition elementConversion: <20% at 200 atmospheres; ～50% at 1000 atmospheres10
10 Nitrogen chemistry: key facts* The manufacture of ammonia—the Haber process Nitrogen and hydrogen are mixed in a 1:3 mole ratio, heated, compressed, and passed over an iron catalyst. The reaction is exothermic, so the greatest equilibrium yield would be given by low temperature conditions. However, the rate is then too slow. At about 500oC 20% of the reactants gases are converted to ammonia and the remainder recycled. It is important to remember that equilibrium is never reached in the Haber process where new reactants are constantly being added and ammonia is constantly being removed. The main uses of ammonia are for fertilizer production (80%), nylons, and nitric acid and explosives. N2 (g)+3H2 (g) → 2NH3 (g) △H= -92 kJ mol-1 Temperature: 500oC Pressure: between 200 and 1000 atmospheres Catalyst: Fe – a transition element Conversion: <20% at 200 atmospheres; ～50% at 1000 atmospheres