WEEK 12 LECTURES
(INORGANIC WEEK 3)
Dr. MD BALA
The bonding between molecules or atoms in the
e.g. sodium chloride
e.g. Graphite or diamond
e.g. copper/gold etc.
Van der Waals bonding
e.g. iodine or benzene
e.g. water and alcohols
Ions stack together in regular
Typically ionic solids.
Have high melting and
They are brittle.
They form electrolyte
solutions if they dissolve
• The attractive force between a pair of oppositely charged ions
increases with increased charge on the ions and with decrease in
requires less energy to
Na+ = 99 pm
requires more energy to
Complete their octets by sharing electron pairs
e.g. Consider F2
The electronic configuration of F is 1s22s22p5
These are combined to form F2.
It is a special case:
• The electrons are considered
to be “delocalized”
• This gives rise to their
properties such as
malleability or ductility.
• Good thermal and
Electrostatic forces and the reason ionic compounds
Electrical conductance and ion mobility
dissolved in water
van der Waals - Due to instantaneous dipoles
• Covalent bonding between unlike atoms results in
unequal sharing of the electrons
– One end has larger electron density than other
• The result is bond polarity
– End with larger e- density gets partial - charge
– End that is e- deficient gets partial + charge
Allotropy and Polymorphism
e.gs. of elements and their allotropes
Bonding in other elements and their chemistries
• Rhombic and monoclinic are
different allotropes of sulfur
(same elements but different structural or molecular units)
Linear molecule with triple bond
Compounds of oxygen (oxides)
Acidity increases left to right
(metals form basic
(non-metals form acidic
Acids and Bases
• Arrhenius definition:
- An acid provides H+ ions (ionizable hydrogen)
and a base produces OH- ions in an aqueous
- An acid is a proton donor and a base is a proton
• Lewis acids and bases:
- An acid is a species that is an e- pair acceptor
and a base is an e- pair donor.
Anhydride means “without water”. A “base without water”
becomes a basic solutione when it reacts with water:
CaO (s) + H2O
Ca2+ (aq) + 2OH- (aq)
The oxide ion is protonated to produce the hydroxide:
O2- + H2O
2OH- (aq) (100%)
A basic oxide reacts with acids to produce water
CaO (s) + 2H+ (aq)
Ca2+ (aq) + H2O (l)
Oxoacids contain H
and O and one other
1. Write a balanced equation for Zn(OH)2 with:
a) an acid
b) a base
2. Does the following species act as an acid, a
base or an amphoteric species?
a) PO43b) CH3NH3+ = CH3NüH2 + H+
Obtained from the dissolution of acidic oxides in water
e.g. CO2 + H2O = H2CO3(aq)
What are some Oxoacids?
What are polyprotic acids?
• They are acids with more than one ionizable
H atom per molecule
phosphoric acid (3 ionizable H
Halogens as oxoacids
E0 = +1.61 V
H O Cl
- the hydrogen in HOCl is attracted to the lone pair on
oxygen atom in water
- water accepts a proton
- HOCl donates a proton
a) What is the oxidation number of Cl in HOCl?
b) What is the oxidation number of Cl in OCl-?
c) What is the oxidation number of Cl in HClO4?
Strengths of oxoacids
• How great is the pull of electrons away from
the O-H bond?
1. The electronegativity of the central atom
2. The no. of terminal O atoms in the acid
H O Cl
H O Br
ENCl = 3.0
ENBr = 2.8
Ka = 2.9 x 10-8
Ka =2.1 x 10-9
Which acid is stronger, H2SO4 or H2SO3?
H O S O H
H O S O H
Which acid is stronger?
H O Cl O
Nitrogen has oxidation nos. from -3 to +5
The most industrially useful states are:
-3 for ammonia NH3
0 molecular nitrogen N2
+5 for nitric acid HNO3
Physical description: NO is colourless,
paramagnetic (1 unpaired e-) and toxic
Generation of NO: Prepared by the action of Cu(II) salts on nitric