Students can go through AP Inter 2nd Year Chemistry Notes 1st Lesson Solid State will help students in revising the entire concepts quickly.
AP Inter 2nd Year Chemistry Notes 1st Lesson Solid State
→ A crystalline solid is one in which the component structural units are arranged in a definite geometrical order characteristic of the substance.
→ Metallic Crystals are opaque, lustrous and are good conductors of heat and electricity.
Ex : Cu, Fe and alloys.
→ Minimum radius ratio, then can give a specific coordination number and hence the shape to the compound.
→ According VBT, proposed by ‘Pauling’, resonance takes place throughout the solid metal.
→ Be, Mg, Cd, Co, Zn, Ti and Tl have ‘hcp’ arrangement of spheres.
→ Na, K, Rb, Cs, Ba, Cr, Mo, W have ‘bcc1 arrangement of spheres.
→ Only known example with simple cubic arrangement is ‘Polonium’.
→ Al, Cu, Au, Pd, Pt, Pb, Ni and Ca have ‘fcc’ arrangement of spheres.
→ Amorphous solids are those substances that do not have sharp melting points. Generally they melt over a range of temperature.
Molten quartz on rapid cooling gives an amorphous solid.
→ Bragg’s equation is nλ =. 2d sin θ
From the relation the conditions for diffraction with max. intensity (i.e., constructive inter-ference) can be calculated.
→ Bragg’s method is used to determine the crystal structures. Bragg’s spectrometer is used for this purpose. But for this method to be used large single crystals are necessary. The planes of the crystal must be fully developed and easily identifiable.
→ Total no.of lattice points in a simple cubic structure = 1 atom.
Total no.of points per unit cell in fee arrangement = 4 atoms.
→ Formula for the calculation of density of unit cell (ρ) is
ρ = \(\frac{\mathrm{ZM}}{\mathrm{N}_{\mathrm{o}} \mathrm{a}^3}=\frac{\mathrm{ZM}}{\mathrm{N}_{\mathrm{o}} \mathrm{V}}\)
Z = no.of atoms per unit cell.
M = Molecular weight,
N0 = Avagadro’s number
a3 (=v) = Volume of unit cell.
→ Schottky defect:
“It is a point defect in which an atom or ion is missing from its normal site in the lattice”.
→ Frenkel defect:
“It is a point defect in which an atom or ion is shifted from its normal lattice position”. The ion or the atom now occupies an interstitial position in the lattice.
→ Interstitial defect:
Some of the constituent particles of solid compound occupy an interstitial site, the crystal is said to have interstitial defect.
→ Schottky and Frenkel defects are point defects. Schottky defect is fouild in highly ionic com-pounds. Frenkel defect is favoured by a large difference in sizes between cation and anion.
→ f – centers are the anionic sites occupied by unpaired electrons.
→ The conductivity in metals depends on the number of valence electrons present per atom.
→ Conductivity of the metals generally decreases as the temperature raises. This is due to increased vibrations in the lattice points.
→ Semi – conductors whose conductivity increases with increase in temperature are called intrinsic semi – conductors.
→ Addition of impurity to the semi conductor to increase the conductivity is known as Doping.
→ Addition of III group elements to Si (or) Ge leads to n – type semi – conductors.
Addition of V group elements to Si (or) Ge leads to p – type semi – conductors.
→ Diamagnetic materials are weakly repelled by the applied magnetic fields.
Ex : NaCl, Benzene etc.
→ Paramagnetic substances are attracted into the applied magnetic field.
Ex : O2, NO, Na-atom etc.
→ Ferromagnetic substances show permanent magnetism even after the applied field is removed. Fe, Co, Ni are the only three elements which show ferromagnetism at room temperature.
→ Fe3O4 shows antiferromagnetism.