Solid State

Question 1

Isomorphic Substances

Answer 1

two or more substances having the same chemical structures. they have the same chemical composition but different atomic ratios

Question 2

Polymorphous Substances

Answer 2

a single substance that occurs in 2 or more forms as a crystal due to differnt conditions

Question 3

Allotropy

Answer 3

polymorphism existing in elements

Question 4

How are crystals classified

Answer 4

ionic, covalent, molecular, metallic

Question 5

How do ionic crystals form

Answer 5

when charged ions are held together by electrostatic force due to oppositely charged ions as cations and anions differ in size.

Question 6

State the properties of an ionic crystal

Answer 6

hard and brittle, have high melting points, bad conductors of electricity in its solid state but good conductors when dissolved in water
like: NaCl, KCl

Question 7

How do covalent network crystals form

Answer 7

when atoms are linked together by covalent bonds resulting in strong & rigid structure as the bonds form a network. the electrons are localized and immobilized

Question 8

State the properties of a covalent network crystal

Answer 8

hard and incompressible, high melting and boiling points, poor conductors of heat and electricity
like: quartz and diamond

Question 9

How do molecular crystals form

Answer 9

when molecules are held together by weak intermolecular forces like weak dipole - dipole interactions, London forces, intermolecular hydrogen bonds.

Question 10

What are molecular crystals

Answer 10

when cl2, ch4, h2, co2 & o2 solidifies and crystalline organic compounds

Question 11

State the properties of a molecular crystals

Answer 11

they are soft, low melting points, poor electric conductors, good insulators

Question 12

How do metallic crystals form

Answer 12

when atoms of the same element held together by a metallic bond

Question 13

State the properties of a metallic crystal

Answer 13

they are malleable, they are ductile, good conductors of heat & electricity
like: Na, K, Fe

Question 14

What is a metallic bond

Answer 14

in a solid state the valence electrons are delocalized over the entire crystal leaving behind a positively charged metal ion (an array of the positive ions immersed in a sea of a mobile electron). these attractive interactions between cations and mobile electrons constitute metal bonds

Question 15

Define lattice

Answer 15

a geometrical arrangement of points in a dimensional periodic array

Question 16

How is a crystal lattice obtained

Answer 16

when a constituent particle to each lattice point forming a basis of crystal lattice

Question 17

Define a crystal

Answer 17

a structure that results by attracting a basis to each lattice point

Question 18

Define unit cell

Answer 18

the smallest repeating structural unit of crystalline solid

Question 19

how is a crystal generated

Answer 19

the space lattice of a crystal is built up of a 3d basic pattern. which is repeated in all dimensions to generate an entire crystal. Unit cells are stacked together to form a crystal. Each unit cell shares faces, edges, and corners with its neighbors.

Question 20

Types of unit cell

Answer 20

1. Primitive unit cell
2. Body centered unit cell
3. Face centered unit cell
4. Base centered unit cell

Question 21

Where are the constituent particles present:
1. Primitive unit cell
2. Body centered unit cell
3. Face centered unit cell
4. Base centered unit cell

Answer 21

1. only at the corners
2. center of a body and corner particles
3. center of each face and corner particles
4. at the center of faces and corner particles

Question 22

Bravais lattices

Answer 22

when these lattices crystal structures of 14 different space lattices in which similar points that can be arranged in a 3d

Question 23

the 7 crystal systems of bravais lattices

Answer 23

1. cubic system
2. Tetragonal system
3. Orthorhombic system
4. Rhombohedral system
5. Monoclinic system
6. Triclinic system
7. Hexagonal system

Question 24

Why do crystal defects occur

Answer 24

They occur during the process of crystallization. when the crystallization occurs at a faster rate. Sometimes they are intentional to create desired properties of a crystal

Question 25

Defne defects

Answer 25

The disorders and irregularities in the arrangements of constituent particles of a solid crystal

Question 26

Define point defects and classify them

Answer 26

irregularities produced in arrangement of basis at the lattice points in crystalline solids. They are classified as:
1. Stochiometric
2. Impurity
3. Non stochiometric