Doubtly
@Doubtly · Joined Feb 2021
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- The density of iridium is 22.4 g/cm3. The unit cell of iridium is fcc. Calculate the radius of iridium atom. Given : Crystal structure of iridium = fcc Molar mass of iridium = 192.2 gmol⁻¹ Density = ρ = 22.4 gcm⁻³ Radius of iridium = ? In fcc struct... 1
- Obtain the relationship between density of a substance and the edge length of unit cell. Consider edge length of cubic unit cell is a, the ∴ Volume of unit cell = a³. Suppose that mass of one particle is m and that there are n pa... 1
- Cu crystallizes in fcc unit cell with edge length of 495 pm. Given : a = 495 pm Radius, r = ? For fcc structure, Radius = r = a/2√(2)= 495/2√(2) = 175pm Ans. Radius of Cu atom = 175 pm. 1
- Cesium chloride crystallizes in cubic unit cell with Cl- ions at the corners and a Cs+ ion in the centre of the cube. Number of Cs⁺ ion at body centre = 1 A Number of Cl⁻ ions due to 8 comers = 1/8×8 = 1 Hence unit cell contains 1 CsCl molecule. 1
- What are the consequences of Schottky defect? Consequences of Schottky defect : As the number of ions decreases, mass decreases. However, volume remains unchanged. Hence, the density of... 1
- What are paramagnetic substances? Give examples. Paramagnetic substances : The magnetic properties of a substance arise due to the presence of electrons. An electron while revolving around... 1
- Calculate the packing efficiency of metal crystal that has simple cubic structure. Packing efficiency of metal crystal in simple cubic lattice : Step 1 : Radius of sphere : In simple cubic unit cell, particles (spheres) are... 1
- How are the spheres arranged in first layer of simple cubic close-packed structures? How are the successive Three dimensional crystal structures are obtained by stacking of two dimensional layers. Simple cubic lattice is obtained by stacking of two... 1
- Calculate the number of atoms in fcc unit cell. Number of atoms in face-centred cubic (fcc) unit cell : In this unit cell, there are 8 atoms at 8 corners and 6 atoms at 6 face centres. Eac... 1
- What are valence band and conduction band? Valence band : The atomic orbitals with filled electrons from the inner shells form valence bands, where there are no free mobile electrons s... 1
- What are ferromagnetic substances? The substances which possess Unpaired electrons and high paramagnetic character and when placed in a magnetic field are strongly attracted an... 1
- Mention two properties that are common to both hcp and ccp lattices. In hcp and ccp ciystal lattices coordination number is 12 and packing efficiency is 74%. 1
- A solid is hard, brittle and electrically nonconductor. Its melt conducts electricity. What type of solid is it? A solid crystalline electrolyte like NaCl is having above properties. NaCl is hard, brittle and electrically nonconductor. But its melt cond... 1
- The picture represents bands of MOs for Si. Label valence band, conduction band and band gap. Conduction band band gap valance band 1
- How does electrical conductivity of a semiconductor change with temperature? Why? Since the energy difference between valence band and conduction band in semiconductor is not large, the electrons from valence band can be p... 1
- What is the unit cell? Unit cell : It is the smallest repeating structural unit of a crystalline solid (or crystal lattice) which when repeated in different direct... 1
- The following pictures show population of bands for materials having different electrical properties Picture A represents metal conductor, Picture B represents insulator, Picture C represents semiconductor. 1
- Which of the three types of packing used by metals makes the most efficient use of fcc has the most efficient packing of particles while scc has the least efficient packing. 1