Presentation on P block elements discusses on 15 th group of friends in the p block of the periodic table.

1. PRESENTED BY S.C.TIWARY, PGT CHEMISTRY,
K.V. AMC, LUCKNOW
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2. GROUP 15 ELEMENTS
Element Symbol Atomic No. Metal or
Non-metal
Nitrogen N 7 Non-metal
Phosphorus P 15 Non-metal
Arsenic As 33 Semi-metal
Antimony Sb 51 Semi-metal
Bismuth Bi 83 Metal
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3. Atomic & Physical Properties
■ Ground state valence shell electronic
configuration ns2np3.
■ The covalent radius increases as we
descend the group.
■ Electro negativities decrease down the
group, except N the rest elements have low
& almost similar electro negativities.
■ Nitrogen is gas, P, As,Sb & Bi are solids
under normal conditions.
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4. OXIDATION STATES
■ Common oxidation states for P & As are –
3, +3 & +5.
■ For Sb & Bi , oxidation states are +3 & +5.
■ The stability of the highest oxidation state
(+5) decreases down the group due to inert
pair effect.
■ The +5 state in Bi is less stable than in Sb.
■ The only well characterized Bi(V)
compound is BiF5
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5. Trends in Chemical Reactivity
■ There is a decrease in covalent character in
the sequence P > As > Sb > Bi.
■ P displays essentially covalent character
although it can accept 3 electrons to form
phosphides.
■ Sb & Bi form M3+ cations due to decrease
in ionization enthalpy.
■ The tendency to form double and triple
bonds relative to single bonds diminishes
markedly.
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6. •P, As & Sb form tetrahedral E4 molecules in
their elemental state containing E-E single
bonds.
•P shows a distinct tendency for catenation
forming both cyclic and open chain compounds
containing P atoms.
•The heavier members can form penta- and
hexa-coordinated derivatives such as PCl5, AsF5
& PF6
-.
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7. Hydrides of Group 15 Elements
■ All elements of group 15 form gaseous
hydrides of the type MH3
■ The stability of the hydrides decreases
sharply down the group.
■ Except NH3, all the hydrides are strong
reducing agents.
■ Except NH3, all the hydrides are highly
poisonous.
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8. •NH3 is associated via H-bonds, while other
hydrides are not associated in the liquid state
and are rather insoluble in water.
•PH3 is a much weaker base than NH3; AsH3,
SbH3 & BiH3 do not show any basic properties.
•These hydrides have a pyramidal structure.
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9. Halides of Group 15 Elements
■ They form two type of halides, MX3 &
MX5
■ Bonding in the trihalo compounds is
predominantly covalent except in BiF3.
■ PCl3 is a colourless liquid, it fumes in
moist air because of its reaction with water
producing HCl.
PCl3 + H2O → H3PO3 + 3HCl
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10. •PCl3 reacts with O2 to form phosphoryl
chloride, P(O)Cl3.
•Tri halides have a pyramidal structure in the
gaseous state.
•E.g. PF3
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11. •PF5 is molecular in both the gaseous & solid
states and has a trigonal bipyramidal structure.
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12. •PCl5 is molecular in the gas and liquid phases
but in the solid state exists as [PCl4]+[PCl6]-
containing tetra and hexa-coordinated
phosphorus species.
•PCl5 is made by the reaction of PCl3 with Cl2 in
CCl4:- PCl3 + Cl2 → PCl5
•PCl5 fumes in air, it reacts with water to give
initially POCl3; if water is excess, the product is
H3PO4. PCl5 + H2O → POCl3 + 2HCl
POCl3 + 3H2O → H3PO4 + 3HCl
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13. Oxides Of Group 15 Elements
■ P, As,Sb & Bi form two types of oxides:-
E2O3 & E2O5.
■ The reluctance of P, As,Sb & Bi to enter
into pπ- pπ multiple bonding leads to cage
structures for their oxides and they exist as
the dimers, E4O6 and E4O10.
■ Bi(V) oxide is unstable.
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14. Structure of P4O6 & P4O10
•P atoms are at the corners of the tetrahedron as in white P.
Six oxygen atoms are along the edges forming P-O-P single
bonds
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15. •Both P4O6 & P4O10 are acidic oxides which
dissolve in water to give Phosphonic acid
(Phosphorous acid) and Phosphoric acid
(orthophosphoric acid) respectively.
P4O6 + 6H2O → 4 H3PO3
P4O10 + 6H2O → 4 H3PO4
•P4O10 is used as a dehydrating agent because of
its great affinity for water. It can dehydrate HNO3
and H2SO4 to yield N2O5 and SO3 respectively.
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16. •The basic nature of the oxides increases with
increasing atomic number.
•P2O3 & As2O3 are acidic; Sb2O3 is amphoteric
and Bi2O3 is basic.
•Bi2O3 dissolves in acids to give salts:
Bi2O3 + 6 HNO3 → 2Bi(NO3) + 3 H2O
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17. OXOACIDS OF PHOSPHORUS
■ Oxoacids are based on tetrahedral four
coordinated P containing at least one P = O
unit and one P – OH group.
■ Examples: - Phosphinic acid, phosphonic acid
& orthophosphoric acid.
■ Two or more P(O)(OH)3 units can join to give
Condensed Phosphoric acids having P-O-P
links. They can have cyclic or linear chain
structures.E.g. Pyrophosphoric acid,H2P2O7
Cyclotrimetaphosphoric acid (HPO3)3 .
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19. PHOSPHINIC ACID
■ Also called
hypophosphorous acid,
H3PO2.
■ It has one P(OH) group
and two hydrogen
directly attached to
phosphorus.
■ It has only one ionisable
H & hence behaves as a
monoprotic acid
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20. PHOSPHONIC ACID
■Also called phosphorous acid, H3PO3.
■It is a diprotic because it contains two
ionisable hydrogen.
■It forms two series of salts, NaH2PO3 &
Na2HPO3 .
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21. ORTHPHOSPHORIC ACID
■ H3PO4, also called
phosphoric acid.
■ It is a triprotic acid.
■ It forms three series
of salts,e.g. NaH2PO4,
Na2HPO4, & Na3PO4.
■ It is used for the
manufacture of
Phosphatic fertilizers.
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22. PHOSPHORUS
■ It occurs as phosphate rock which consists of
the minerals hydroxyapatite and florapatite.
■ It is present in bones and in living cells.
■ Elemental P is obtained by the reduction of
calcined phosphate rock with coke and
sand.The P vapour thus obtained is condensed
to a solid and stored under water to protect it
from reaction with air.
■ 2Ca3(PO4)2 + 6SiO2 +10 C → P4 + 6CaSiO3 +10CO
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23. Allotropy of Phosphorus
■ White Phosphorus
■ Red phosphorus
■ Black phosphorus
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24. White Phosphorus
■ It is formed by condensation from the
gaseous or liquid states.
■ It is a waxy solid, insoluble in water but
highly soluble in CS2 & benzene.
■ It is highly reactive and spontaneously
ignites in air. Hence it is stored under water.
■ It glows in dark and this property gives the
element its name PHOSPHORUS (Greek for
light bringing)
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25. •White P consists of discrete P4 molecules in
which the 4 P atoms are at the corners of a
tetrahedron and each P atom is covalently linked to
the other three P atoms.
•It is also known as
yellow phosphorus.
•It is highly toxic.
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26. Red Phosphorus
■ When white P is heated at 570 K in an inert
atmosphere for several days, it gets
converted into red phosphorus.
■ It has higher melting point and greater
density than white P.
■ It is much less reactive than white P.
■ It is essentially non-toxic.
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27. •It is amorphous and has a polymeric
structure.
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28. Black Phosphorus
■ It is thermodynamically most stable form
of P.
■ It is obtained by heating white phosphorus
at 470 K under high pressure. A series of
phases of black phosphorus are formed.
■ One of these phases consists of an extended
layer structure in which each P is bound to
three neighbours by single bonds.
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29. Uses of phosphorus & its compounds
■ Used in the manufacture of (i) phosphatic
fertilizers, (ii) food-grade phosphates, (iii)
detergent phosphates &
(iv) pharmaceuticals.
■ Elemental phosphorus is used in water
industry and is the starting material for the
manufacture of organo-phosphorus
compounds used as pesticide
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