p block, group 15, class 12 chemistry, class 11 chemistry, nitrogen family

1. Group 15 elements :
The NITROGEN Family
-Puneeta Malhotra

2. Group 15
• Group 15 or the Nitrogen family has Nitrogen
(N) , Phosphorous (P) , Arsenic (As)
,Antimony(Sb) , Bismith (Bi) .
• Nitrogen comprises 78% by volume of the
atmosphere

3. Electronic Configuration
• General electronic configuration ns2np3
• Oxidation state -3, +3 and +5
• Stability of +5 OS decreases as we
move down the group due to inert pair effect.

4. What is Inert Pair Effect ?
• Reluctance of ns2
electrons to take
part in bonding due
to the poor shielding
effect of intervening
d and f orbitals on
moving down the
group is known as
Inert Pair Effect .

5. ATOMIC SIZE

6. Atomic Radii
• Atomic Radii (pm)
• N 70
• P 110
• As 121
• Sb 141
• Bi 148
• On moving down the group atomic radius
is expected to increase.
• Across the period atomic radii decrease
• As to Bi only a small increase in radius is observed
due to ineffective shielding of filled d and/or f
orbitals

7. Ionization Enthalpy
• The ionization enthalpy values decreases down
the group due to increase in size.
• IE1<IE2<IE3
• Group 15 elements have higher IE than group 14
and group16 due to stable half filled
configuration

9. Electronegativity
• Down the group, electro negativity decreases
• N is most electronegative element of the group
• N forms Hydrogen bonds

10. Physical Properties
• All the elements of this group are polyatomic.
Except nitrogen, all the elements show
allotropy and catenation
• Exception: N is diatomic as N-N is weak due to
interelectronic repulsion of lone pair
• Metallic character increases down the group
due to decrease in ionisation enthalpy and
increase in atomic size. N, P are non metals,
As Sb metalloids and Bi metal

11. Oxidation State And Trends In
Chemical Reactivity
• Show OS -3, +3 and +5
• tendency to exhibit –3 oxidation state decreases
down the group due to increase in size and
metallic character.
• The stability of +5 oxidation state decreases and
• that of +3 state increases (due to inert pair
effect) down the group. Bi only forms BiF5
• Nitrogen undergoes dispropornation
• 3HNO2 → HNO3 + H2O + 2NO

12. • Due to small size, high elecrtonegativity, high IE and
non availability of d orbitals
• N2 is unreactive (inert) due to strong pπ –pπ
• Other elements of group donot form strong pπ –pπ
as their atomic orbitals are large and diffuse so they
cannot have effective overlapping
• nitrogen cannot form dπ –pπ and dπ –dπ bond and
maximum covalency of 4 : due to non availability
of d orbitals Nitrogen cannot form R3P = O type
compounds, or R3P = CH2 (R = alkyl group).
Phosphorus, NCl5 not formed

13. Reactivity Towards Hydrogen
• hydrides have formula EH3
• Bond dissociation enthalpy decreases down the
group. Small size N overlaps better with H and
overlap becomes less effective with increase in size
of atom.
• The stability of hydrides decreases from NH3 to
BiH3 due to decrease in bond dissociation enthalpy
• the reducing character of the hydrides increases
down the group due to decrease in bond dissociation
enthalpy. BiH3 is a strong reducing agent

14. • All hydrides are Lewis bases due to presence of lone pair
of electrons
• Basicity decreases in the order NH3 > PH3 > AsH3 >
SbH3 > BiH3 as The electron density on central atom
decreases down the group due to increase in size of
central atom
• Bond angle decreases down the group Since nitrogen
atom is highly electronegative. So in NH3 there is high
electron density around the N atom which causes greater
repulsions between the electron pairs around the N atom
resulting in maximum bond angle. Since
electronegativity decreases down the group, the electron
density also decreases and consequently the repulsive
interactions between the electron pairs also decrease
thereby decreasing the bond angle H-M-H.
• Ammonia has higher bp than PH3 and AsH3 though bp
increase down the group due to strong hydrogen
bonding in NH3

15. Reactivity Towards Oxygen
• Form oxides with formula E2O3 and E2O5
• The oxide in the higher oxidation state of the
element is more acidic than that of lower oxidation
state
• acidic character decreases down the group because
metallic character increases
• NO2 dimerise as NO2 contains odd number of
valence electrons. On dimerisation, it is converted to
stable N2O4 molecule with even number of
electrons and is stable.
• covalence of nitrogen in N2O5 is 4

16. Reactivity Towards Halogens
• Form Halides with formula EX3 and EX5.
• Nitrogen does not form pentahalide due to non-
availability of the d orbitals in its valence shell.
• Pentahalides are more covalent than trihalides. Higher
the positive oxidation state of central atom, more will be
its polarising power which, in turn, increases the
covalent character of bond formed between the central
atom and the other atom.
• All the trihalides of these elements except those of
nitrogen are stable. In case of nitrogen, only NF3 is
known to be stable.
• Trihalides except BiF3 are predominantly covalent in
nature. Bi is metallic in nature

17. White P
• Less stable, more
reactive due to angular
strain in the P4
molecule where the
angles are only 60°.
• Glows in dark
• poisonous
• Discrete molecule
Red P
• More stable, less
reactive
• Does not glow in dark
• Not poisonous
• polymeric

19. • P-H bond is responsible for reducing character
• H3PO2 good reducing agent due to 2 P-H bonds
• Basicity (or n factor) depends no. of P-OH bonds
• H3PO2 is monobasic, H3PO3 is dibasic and
H3PO4 is tribasic
• Oxoacids in +3 OS disproportionate
• 4 H3PO3 3 H3PO4 + PH3

20. Thank You