Monday, 19 December 2016
Wednesday, 20 January 2016
Tuesday, 19 January 2016
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.
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
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.