Solids

Question 1

Features of covalent bonds

Answer 1

Strong

Highly directional

Question 2

Features of ionic bonds

Answer 2

Strong
Purely coulombic
Between permanently charged atoms

Question 3

Features of van der waals bonds

Answer 3

Between atoms with no net charge

Weak

Question 4

Finding min separation

Answer 4

Differentiate van.d.waals potential

Question 5

Cohesive energy and elements

Answer 5

Energy required to separate a crystal

1. Ionisation energy
2. Electron affinity
3. Coulomb interaction

Question 6

lattice

Answer 6

array of discrete points, same from every angle

Question 7

Primative lattice vectors

Answer 7

any vector joining two points on a lattice

Question 8

Unit cell

Answer 8

building block of the crystal

encloses minimum lattice points

Question 9

Basis

Answer 9

arrangement of atoms at the lattice points

Question 10

Arrangement of hexagonal close packing and coordination number

Answer 10

b on a on b - 12

Question 11

Arrangement of face centered cubic packing and coordination number

Answer 11

b on a on c - 12

Question 12

Definition of packing fraction

Answer 12

ratio of volume of spheres to volume of cube

Question 13

limiting distance for FCC

Answer 13

face diagonal

Question 14

limiting distance for BCC

Answer 14

body diagonal

Question 15

requirement for diffraction

Answer 15

wavelength similar to spacing

Question 16

Finding miller indices

Answer 16

1. Find intercepts
2. Reciprocate them
3. Clear reciprocal of fraction

Question 17

Definition of reciprocal lattice

Answer 17

set of imaginary points perpendicular to real space planes

Question 18

Relationship between spacing and reciprocal length

Answer 18

inversely proportional

Question 19

Advantages of x-rays

Answer 19

easily available
high penetrating power
similar wavelength

Question 20

Disadvantages of x-rays

Answer 20

can destroy fragile samples

restrictive single wavelength

Question 21

Advantages of neutrons

Answer 21

higher sensitivity to light
strong magnetic interactions
low energies

Question 22

Disadvantages of neutrons

Answer 22

expensive
dim sources
resolution is poor

Question 23

Types of defects

Answer 23

Grain boundaries
Dislocations
point defects

Question 24

Dealing with polyatomic lattice vibrations

Answer 24

as a coupled oscillator