Wednesday, 20 January 2016
Tuesday, 19 January 2016
CHAPTER-1 SOLID STATE
As we know that matter exists in different physical states under
different conditions of temperature and pressure. For example solid state,
liquid gases plasma and BEC etc. Now we will study about different aspects of
solid state.
Introduction:
1. The
state of matter whose M.P is above room temp is solid state. Solids have
definite shape and volume, having high density and constituent particles are
held strongly.
2. Based
on arrangement of particles types of solid :
1:
Crystalline 2: Amorphous
3. Crystalline
solids have regular arrangement of constituent particles throughout, melting
point is sharp, Anisotropic in nature and give clear cut cleavage.
4. Amorphous
solids have no regular arrangement, no sharp M.P, isotropic in nature they do
not exhibit cleavage property.
5. Amorphous
silica is used in photovoltaic cells.(Applications of amorphous solid)
6. Space
lattice is the regular 3D, arrangement of constituent particles in the
crystalline solid. It shows how the constituting particles
(atoms, molecules etc.) are arranged.
7. Smallest
repeating unit in a space lattice is called unit cell.
8. There
are 4 types of unit cells, 7 crystal systems and 14 bravais lattices.
9. Types
of unit cell No.
of atoms per unit cell
i. Simple cubic
unit cell 8*1/8=1
ii. FCC (Face
centered cubic) 8*1/8+6*1/2=4
iii. BCC (Body
centered cubic) 8*1/8+1*1=2
10. Hexagonal
close packing and cubic close packing have equal efficiency i.e 74%
11. Packing
efficiency =volume occupied by spheres (Particles)/volume of unit cell *100
12. For
simple cubic unit cell the p.f.=1*4/3 *πr3/8*r3
*100 =52.4
13. The packing efficiency in fcc =4*4/3 *πr3/16*2 1/2 r3
*100 =74
14. The packing efficiency in bcc =2*4/3 *πr3/64*33/2 r3
*100 =68
15. The packing efficiency in hcp =74
16. Packing
efficiency in bcc arrangement in 68% and simple cubic unit cell is 52.4%
17. Unoccupied
spaces in solids are called interstitial voids or interstitial sites.
18. Two
important interstitial voids are (I). Tetrahedral void and (II). Octahedral
void.
19. Radius
ratio is the ratio of radius of void to the radius of sphere.
a. For
tetrahedral void radius ratio=0.225
For octahedral void radius ratio=0.414
For octahedral void radius ratio=0.414
20. No.
of tetrahedral void=2*N (N=No. of particles)
21. No.
of octahedral void=N
22. Formula
of a compound depends upon arrangement of constituent of particles.
23. Density
of unit cell
|
Density =
|
a3xNA
D=density, M=Molar mass, a=side of unit
cell, NA=6.022 x1023
24. The
relationship between edge length and radius of atom and interatomic or
interionic distance for different types of unit is different as given below
a. Simple
cubic unit cell a=2R
b. F
C C a=4R/
c. B
C C a=4R/
25. Interatomic
distance=2R
26. Interionic
distance= Rc+Ra (Rc=Radius of cation, Ra=Radius of anion)
27. Imperfection
is the irregularity in the arrangement of constituent particles.
28. Point
defect or Atomic defect-> it is the deviation from ideal arrangement of
constituent atom. Point defects are two types (a) Vacancy defect (b)
Interstitial defect
29. Vacancy
defect lowers the density and
30. Interstitial
defect increases the density of crystal.
31. Point
defects in the ionic crystal may be classified as:
a. Stoichiometric
defect (Ratio of cation and anion is same).
b. Non
Stoichiometric defect (disturb the ratio).
c. Impurity
defects (due to presence of some impurity ions at the lattice sites)
32. Schottky
defect lowers the density of crystal it arises due to missing of equal no. of
cations of anions from lattice sites e.g. Nacl.
33. Frenkel
defectis the combination of vacancy and interstitial defects. Cations leave
their actual lattice sites and come to occupy the interstitial space density
remains the same eg. Agcl.
34. Non
stoichiometric defect
a. Metal
excess defect due to anion vacancy.
b. Metal
excess due to presence of interstitial cation.
c. Metal
deficiency due to absence of cation.
Subscribe to:
Posts (Atom)