solids, crystalline solids, crystals, ions, sodium chloride

1. TYPES OF
CRYSTALLINE
SOLIDS
CHAPTER # 6 SOLIDS
CHEMISTRY XI FDC

2. CRYSTALLINE SOLID:
Crystalline solids are well-ordered, have
definite arrangements of molecules, atoms
or ions.

3. UNIT CELL
The smallest repeating unit in a crystal is
a unit cell.
Unit cell is the smallest unit with all the
symmetry of the entire crystal.

4. CRYSTAL LATTICE
An array of points representing the
arrangement of particles in three
dimensional spaces is called crystal lattice.

5. A lattice is of 3 types:
CRYSTAL LATTICE

7. I) LOCATION OF IONS:
In NaCl, Na+ ions are so located that there
are six Cl- ions around it and vice versa.
The size of Na+ ion is smaller than Cl- ion.

8. II) CO-ORDINATION NUMBER:
The no. Of anions which contact a unit cation
is called it’s co-ordination number.
In NaCl, co-ordination number is 6.

9. III) NO. OF NaCl IN EACH UNIT:
In NaCl there are 8 Cl- ions at each
corner of the cube.
Each corner ion is shared
between eight unit cells, each face shares
with two unit cells.

10. Cl- Ions (Green)
8 at corners = 8/8 = 1
6 at face centers = 6/2 = 3
Total = 1+3 = 4
Na+ Ions (Violet)
12 at edge centers = 12/4 = 3
1 at body center = 1
Total = 3+1= 4
4Na+ + 4Cl-  4 NaCl

11. DIFFERENT TYPES OF PACKING
ARRANGEMENTS IN UNIT CELLS

12. OPEN PACKING – SIMPLE CUBE

13. CLOSE PACKING – 2 WAYS
(HCP OR CCP)

14. HEXAGONAL CLOSE PACKING (HCP)
– ABAB TYPE

15. CUBIC CLOSE PACKING (CCP) –
ABCABC TYPE

16. CRYSTALLINE
SOLIDS - TYPES
On basis of bonding/attraction
forces:
1. IONIC CRYSTALS
2. COVALENT CRYSTALS
3. METALLIC CRYTALS
4. MOLECULAR CRYSTALS

17. 1. IONIC CRYSTALS
An ionic solid is a solid that
consists of cations and anions
held together by electrical
attraction of opposite charges
(ionic bond).
Example: NaCl (Rock Salt)

18. IONIC CRYSTALS
High melting points
Hard and brittle
Conduct electricity
only in their molten
state (or solution)
Thermally stable

19. 2. COVALENT CRYSTALS
A covalent network solid is
a solid that consists of atoms
held together in large
networks or chains by
covalent bonds.

20. COVALENT CRYSTALS
High Melting points
Hard & Rigid
Giant covalent
network structure
Bad conductors of
electricity (Except
Graphite)
High latent heat of
fusion
Low coefficient of
expansion

21. 3.METALLIC CRYSTALS
A metallic solid is a solid
that consists of positive
cores of atoms held
together by a surrounding
“sea” of electrons (metallic
bonding).

22. METALLIC CRYSTALS
High Melting Point
High Conductivity
Lustrous
Malleable & Ductile

23. 4.MOLECULAR CRYSTALS
A molecular solid is a
solid that consists of
atoms or molecules held
together by intermolecular
forces.

24. Weak
intermolecular
attractions
Low melting
points (below
300oc).
Soft & brittle
Nonconductors.
MOLECULAR SOLIDS