The document discusses different types of bonding: ionic, covalent, and metallic. Ionic bonding involves the transfer of electrons between metals and non-metals to form ions. Covalent bonding involves the sharing of electron pairs between non-metals. Metallic bonding involves a sea of delocalized electrons that are attracted to cationic metal ions arranged in a lattice. Each type of bonding results in different material properties depending on whether electrons are transferred, shared, or free to move.
4. Ionic bonding is the transfer of electrons from
one atom to another to achieve an inert gas
configuration, forming ions.
Ionic bonds are formed between METALLIC and
NON- METALLIC atoms ONLY.
- Metals lose electrons to form positive ions
(cations)
- Non-metals gain electrons to form negative ions
(anions)
5. An ionic bond is an attraction between
oppositely charged ions, which are formed by
the transfer of electrons from one atom to
another.
E.g. In sodium chloride, each sodium atom
transfers an electron to a chlorine atom. The
result is a sodium ion and a chloride anion.
These two ions attract each other to form a
stable compound.
6.
7. Ionicsubstances appear as giant
lattice structures in which the
ions are held together by
electrostatic force between
oppositely charged ions. To find
the formula of ionic bond, say
sodium chloride bond, by
looking at lattice structure, we
count the ratio of amount of
metal ions to non-metal ions. E.g.
in sodium chloride, the ratio Na:Cl
is 1:1, therefore the ionic formula
8. Since ions are held strongly in place by the other
ions, they cannot move or slip over each other
easily and are hence hard and brittle.
Melting and boiling point
• The attraction between opposite ions is very
strong. A lot of kinetic energy is thus
required to overcome them and the melting
point and boiling point of ionic compounds is
very high.
9. Since ionic solids contain ions, they are
attracted by electric fields and will, if possible,
move towards the electrodes and thus conduct
electricity. In the solid state, however, the ions
are not free to move since they are tightly held
in place by each other. Thus ionic compounds do
not conduct electricity in the solid state. Ionic
solids are thus good insulators.
In the liquid(aqueous or molten) state, the ions
are free to move and so can move towards their
respective electrodes. Thus ionic compounds can
conduct electricity in the liquid state.
10. Ioniccompounds are soluble in water but
insoluble in organic compounds. This is
because the ions attract water molecules
which distrupts the crystal structure,
causing them separate & go into solution.
11. Covalent bonding is the sharing a pair of
electrons to gain electronic configuration of
an inert gas, usually for molecules.
Covalent bonds occur between NON-
METALLIC ATOMS ONLY.
In covalent bond, we try to substitute
the short of electrons of two/more atoms
between each other to form the 2 or 8
valence electrons (noble gas structure). The
shared electrons appear in pairs.
12. A pair of shared electrons between 2 atoms
forms Single bond, X – Y.
Two pairs of shared electrons between 2
atoms forms Double bond, X = Y.
Three pairs of shared electrons between 2
atoms forms Triple bond, X = Y.
This
information is important when you
want to know the bond forces between
atoms in exothermic/endothermic reactions.
13.
14. Electrical conductivity
There are no ions and no delocalised electrons, so
there is little electrical conductivity in either solid
or liquid state.
Structure
The intermolecular forces are weak and generally
non-directional, so most molecular covalent
substances are soft, crumbly and not very strong.
15. Melting and boiling point
These are generally low, since intermolecular forces
(Vander Waal’s forces)are weak. Intermolecular
forces also decrease rapidly with increasing
distance, so there is often little difference in the
melting and boiling points.
16. Silicondioxide, SiO2, has silicon atoms
bonded with another oxygen atoms in a
tetrahedral arrangement which each silicon
atom uses all its valence electrons to form 4
single covalent bonds with other 4 oxygen
atoms.
17. Diamond
•Diamond has carbon atoms
bonded with other carbon
atoms in a tetrahedral
arrangement in which each
carbon atom uses all its
valence electrons to form 4
single covalent bonds with
other 4 carbon atoms.
18. Graphitehas flat layers of carbon atoms
bonded strongly in hexagonal arrangement in
which the layers are bonded to each other
weakly.
19. It is a hard solid because it consists of
many strong covalent bonds between atoms.
This property makes it suitable as abrasives.
It has very high melting and boiling points.
It does not conduct electricity (except
graphite) because there are no free electrons
in covalent bonds since they are used to
form bonds; hence electrons are in fixed
positions. To conduct electricity, there must be
free electrons.
All covalent structures are insoluble in water.
20. Metallicbonding is the attraction between
cations and a sea of delocalised electrons.
The cations are arranged to form a lattice,
with the electrons free to move between
them.
Thestructure of the lattice varies from
metal to metal, and they do not need to be
known in detail .The generalised structure
can be drawn as follows:
21.
22. Metals can be bent (ductile) and can be stretched (malleable)
because the layers of atoms in metals slide over each other
when force is applied but will not break due to attractive force
between electrons and metal ions.
2. Metals conduct electricity as it has free electrons which carries
current.
3. Metals conduct heat as it has free electrons which gains
energy when heated and moves faster to collide with metal
atoms, releasing heat in collisions.
4. Metals have high melting and boiling points because the
bonds between metals is very strong. Hence very high heat energy
is needed to break the bonds.