Transcript Document

The P Block
Nitrogen and Group 5
P block group V 1
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 2
14.0
7
31.0
15
74.9
33
121.8
51
209.0
83
N Nitrogen
[He] 2s22p3
P Phosphorus [Ne] 3s23p3
As Arsenic
[Ar] 3d104s24p3
Sb Antimony
[Kr] 4d105s25p3
Bi Bismuth
145d106s26p
4f
[Xe] 3
P block group V 3
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 4
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 5
Ammonia
• Ammonia is nitrogen
hydride, NH3
• Lone pair not
involved in bonding
H
..
N
H
H
– Dative covalent
bonds (dcb’s)
possible
P block group V 6
Ammonia
• NH3 is a base and
forms dcb’s to H+ ions
to give ammonium ions
(NH4+)
H
H
N
+
H
H
– 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 7
Nitrogen Oxides
Name /
Formula
• Nitrogen
monoxide
• NO
Appearance Where it comes
from
• Colourless • Combustion
gas, turns
processes
to brown
• Thunderstorms
NO2 in air • Formed in the soil
by denitrifying
bacteria
P block group V 8
Nitrogen Oxides
Name /
Formula
• Nitrogen
dioxide
• NO2
• Dinitrogen
oxide
• N2O
Appearance Where it comes
from
• Brown gas • From oxidation of
(toxic)
NO in the
atmosphere
• Colourless
gas
• Formed in the soil
by denitrifying
bacteria
P block group V 9
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 10
Bonding in Nitrates
Nitrate(III)
O
N
••
O
Nitrate(V)
-
-
O
O
N
O
By using its lone pair to
The charge is
a dative covalent bond
delocalised over the
two N-O bonds, which to an oxygen atom,the
nitrogen increases its
are equivalent
oxidation state to +5
P block group V 11
Nitrates
Name and
Formula
Commonly Properties
called
•Nitrate(V) ion
•NO3-
•Nitrate
•Nitrate(III) ion
•NO2-
•Nitrite
• Oxidising agent
• Metal nitrate(V)
compounds are very
soluble in water
• Can be reducing or
oxidising agent
• Metal nitrate(III)
compounds are
soluble in water
P block group V 12