P block group V 1

The P The P BlockBlock

Nitrogen and Group 5

P block group V 2

Group 5Group 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

14.0

N Nitrogen[He]

2s22p37

31.0

P Phosphorus

[Ne]

3s23p3

15

74.9

As Arsenic[Ar]

3d104s24p3

33

121.8

Sb Antimony

[Kr]

4d105s25p3

51

209.0

Bi Bismuth[Xe]

4f145d106s26p3

83

P block group V 4

Group 5Group 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

NitrogenNitrogen

• 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

AmmoniaAmmonia

• Ammonia is nitrogen hydride, NH3

• Lone pair not involved in bonding– Dative covalent

bonds (dcb’s) possible

N HH

H

..

P block group V 7

AmmoniaAmmonia• 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!!)

+N HH

H

H

P block group V 8

Nitrogen OxidesNitrogen Oxides

Name / Name / FormulaFormula

AppearanAppearancece

Where it comes Where it comes fromfrom

•Nitrogen monoxide•NO

•Colourless gas, turns to brown NO2 in air

•Combustion processes•Thunderstorms•Formed in the soil by denitrifying bacteria

P block group V 9

Nitrogen OxidesNitrogen Oxides

Name / Name / FormulaFormula

AppearanAppearancece

Where it comes Where it comes fromfrom

•Nitrogen dioxide

•NO2

•Brown gas (toxic)

•From oxidation of NO in the atmosphere

•Dinitrogen oxide

•N2O

•Colourless gas

•Formed in the soil by denitrifying bacteria

P block group V 10

NitratesNitrates

• 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

Bonding in NitratesBonding in Nitrates

O

O

NO

-

By using its lone pair to a dative

covalent bond to an oxygen atom,the

nitrogen increases its oxidation state

to +5

Nitrate(V)

The charge is delocalised over the

two N-O bonds, which are equivalent

Nitrate(III)

-

NOO

••

P block group V 12

NitratesNitratesName and Formula

Commonly called

Properties

•Nitrate(V) ion

•NO3-

•Nitrate •Oxidising agent•Metal nitrate(V) compounds are very soluble in water

•Nitrate(III) ion

•NO2-

•Nitrite •Can be reducing or oxidising agent

•Metal nitrate(III) compounds are soluble in water