The P Block

1. The P Block Nitrogen and Group 5 P block group V

2. Group 5 • Is at the centre of the periodic table • Top of group, non-metals: • Nitrogen and Phosphorus • Bottom of group, metalloids (metallic elements with non-metal character): • Antimony and Bismuth P block group V

3. P block group V

4. Group 5 • Group 5 elements can form 3 covalent bonds • Sharing the 3 unpaired electrons • Gives compounds with oxidation state of +3 or –3 for group 5 element • Each atom has a lone pair of electrons • Enables atoms to form dative covalent bonds • When they do this Group 5 elements can form some compounds with oxidation state of +5 for the Group 5 element P block group V

5. Nitrogen • Very abundant element • Very unreactive! • N2 unreactive because of strong triple bond holding N’s together • Bond enthalpy of N N is +945 kJ mol-1 (Bond enthalpy of N-N is +158 kJ mol-1) • Hence most reaction of N2 have high EA and require high T and catalysts to make them occur • Haber process- high T + Fe catalyst…. • Lightning or >2000ºC to make N2 react with O2 P block group V

6. .. Ammonia • Ammonia is nitrogen hydride, NH3 • Lone pair not involved in bonding • Dative covalent bonds (dcb’s) possible P block group V

7. + Ammonia • NH3 is a base and forms dcb’s to H+ ions to give ammonium ions (NH4+) • Remember once dcb’s formed no different from cb’s! • NH3 also forms dcb’s with TM ions and is a good ligand in complexes (see earlier!!) P block group V

8. Nitrogen Oxides P block group V

9. Nitrogen Oxides P block group V

10. Nitrates • 2 Kinds of nitrate ions involved in the nitrogen cycle: • Nitrate(III), NO2- • Nitrate(V), NO3- • Both are called nitrates, but distinguished by showing OS of N P block group V

11. Nitrate(III) Nitrate(V) - - •• The charge is delocalised over the two N-O bonds, which are equivalent By using its lone pair to a dative covalent bond to an oxygen atom,the nitrogen increases its oxidation state to +5 Bonding in Nitrates P block group V

12. Nitrates P block group V