Solid state part 2 | Chemistry Class 12 | By Mrs. Shubhada Walawalkar

UNIT: 1
SOLID STATE
Part-II
1.3 classification of crystalline solids.
Marks 4-6
Sou S.S.Walawalkar - N.S.P.Jr.college.Devgad

Classification of Solids
SOLIDS
CRYSTALLINE
MOLECULAR
POLAR NON-POLAR
HYDROGEN
BONDED
IONIC METALLIC
COVALENT or
Network
solids.
AMORPHOUS

1.3 Classification of Crystalline Solids
➢Metallic Solids like Au, Pt, Ag, Cu, Zn are crystalline
solids;
➢inorganic salts like NaCl, MgSO₄, KBr, CuSO₄ are
crystalline solids;
➢non-metallic solids like S, P, I are crystalline solids;
➢Organic substances like benzoic acid, oxalic acid,
camphor, naphthalene are also crystalline solids

All these crystalline solids exhibit different physical
properties & formed by different types of intermolecular
forces of attraction.
They are classified into 4 main types
1. Ionic Solids
2. Covalent net work solids
3. Metallic solids
4. Molecular Solids

1.3.1. Ionic Solids
✓All salts are crystalline and called Ionic Solids.
✓ Ionic salts are formed by Molecules containing positively
charged, small sized cations & -vely charged relatively
Bigger anions.
✓The charges on ions & arrangement of ions balance each
other & molecule is electrically neutral.
✓E.g.

1.3.1 Ionic Solids(continued)-
➢3D arrangement of Cations & Anions in crystalline
solid is such that, opposite forces are completely
compensated
➢ Electrostatic forces of attraction between nearest
neighboring ions are very strong
➢So crystalline solids are hard & brittle, On application
of shearing force, ionic crystals undergo distortion &
fracture in crystal structure

1.3.1 Ionic Solids(continued)-
➢posses higher MPs, in solid state non-conductors of
electricity, as free electrons are not available
➢In fused state/ in aqueous solution, ions are available
for conduction of electricity

1.3.2 Covalent net work solids
➢Constituent particles are atoms
➢Atoms are linked by covalent bonds
➢ Due to continuous three dimensional covalent bonding
rigid net work is formed results in formation of giant
molecule.
➢ These are hard or brittle due to covalent bonding
between the atoms & possess high M.P. and B.P
➢Electrons are localized hence not mobile
➢These are poor conductors of heat and electricity or act as
insulators.
➢E.g.- 3 allotropes of carbon- diamond, graphite &
fullerene

a) Diamond-
➢ It is precious crystal used in jewellery.
➢ C-atoms are sp3 hybridized &
covalent bonding is continues in all
directions to form a big giant network
of covalent solids
➢Strong covalent bonds between sp3
hybridized C-atoms make diamond very
strong & hardest solid with very high MP
of 3550⁰C

b) Graphite-
➢ C-atoms are sp2 hybridized.
➢ Each C-atom is covalently bonded to 3 other sp2
hybridized C-atoms to form interlinked 6 membered
rings of C-atoms
➢remaining half filled un-hybridized 2Pz orbital used for
Pi-bonding, so that layers of C-atoms i.e. graphite are
formed.
➢ It has delocalized molecular orbitals & delocalized
electrons have freedom to move in delocalized molecular
orbitals. good conductor of electricity

➢ adjacent layers of C-atoms held together by weak
van der Waal’s forces of attraction.
➢ These layers can slide over another layer
➢ used as lubricant for reducing friction,
used in ribbons for printing in computers,
typewriters & in lead pencils

c) Buckminster
fullerene/buckball/fullerene-
- Have formula C₆₀, have a shape
of soccer ball is hollow sphere
- On sphere, there are 60
equidistant spaces occupied by
carbon atoms
- C-atoms are sp2 hybridized,
delocalized molecular orbits are
spread over complete structure
of fullerene
- Structure is formed by
arranging C-hexagons & C-
pentagons

➢ Tubes made from
fullerene & graphite
are called
Nanotubes & used
as high strength
materials, electric
conductors,
molecular sensors &
semiconductors

1. 3.3Molecular Solids
✓ . Constituent particles are molecules (or unbonded
single atoms )of the same substance
✓ The bond within molecules are covalent
✓ These are soft substances with low m.p.
✓ These are poor electric conductor and good insulators.
✓these are classified in 3 types depending upon
Nature of intermolecular forces of attraction between
neighboring molecules
1)Polar molecular solids –weak dipole -dipole interaction
2)Non polar molecular solids-weak dispersion or London
forces
3)Hydrogen bonded solids – Hydrogen bonds

Molecular Solids
1)Polar molecular solids –weak dipole -dipole interaction
posses permanent dipole moment
e.g. solid HCL,H2O,SO2,
There is separation of +ve & -ve charges & arrange themselves
such a way that opposite charges of neighboring molecules
brought closer

2)Non polar molecular solids-weak dispersion or
London forces e.g.H2,CH4,He,Ar,Ne (monoatomic
solids)
3)Hydrogen bonded solids – Hydrogen bonds e.g.H2O,
NH3, Hf

3) Hydrogen Bonded Molecular Solids
➢ Hydrogen bonds e.g.H2O, NH3, Hf
If hydrogen atom in a molecule is bonded covalently to
strongly electronegative atom like O₂, N₂, F₂, then H-atom
acquires additional positive charge & shows ability to form
additional bond with electronegative atom in the vicinity.
This is called Hydrogen Bonding.

1.3.4 Metallic Solids-
➢Metallic solids are crystalline solids formed by atoms
of same metallic element held together by metallic
bond.
➢Valance electrons are delocalized over the space of the
crystal & have freedom to move from one end to
other.
➢All valance electrons of metal atoms constitute a sea of
electrons & metal atoms are in the form of +ve ions

❖ Force of attraction between +vely charged metallic
ion & -vely charged sea of delocalized electrons
within the sphere of influence is called metallic bond
❖ Valence electrons are not confined to one place &
not restricted to any 1 metal ion

1.3. 4 Metallic Solids (Continued)-
✓If energy is supplied, valence electrons move from 1
place to another
✓These mobile electrons make all the metals good
conductor of heat & electricity
✓ On applying shearing force the layers slide on one
another & structure do not fracture hence malleable,
ductile

▪ Metallic bonds are stronger than ionic & covalent
bonds, tougher than other solids
▪ Metal is present in the form of several layers
arranged over one another
▪ Metals are malleable & ductile. Two/more metals can
be alloyed together, which exhibit all the properties of
metal
▪ The surfaces of metals exhibit luster of grey/silvery
colour Au- Yellow luster, Cu- Reddish luster

THANK YOU!

Solid state part 2 | Chemistry Class 12 | By Mrs. Shubhada Walawalkar

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