Unit 2 - Atomic Bonding and Structure

Question 1

4 properties of atoms

Answer 1

1. Indivisible and indestructible
2. All atoms of an element are identical
3. Atoms of different elements have different weights and chemical properties
4. A chemical reaction is a rearrangement of atoms

Question 2

Primary Bonding

Answer 2

sharing or donating electron between atoms to form a more stable electron configuration

Question 3

Secondary Bonding

Answer 3

Weak compared to primary bonds. They occur when there are dipoles in molecules

Question 4

Sub-divisions of Primary Bonds

Answer 4

1. Covalent - sharing electrons in saturated bonds
2. Ionic - isolated ions only exist in gaseous form, the bonds exert forces in all directions
3. Metallic - Electrons share orbitals with multiple atoms

Question 5

Materials Characteristics for Covalent bonds (4)

Answer 5

For a solid;
V. High elastic Modulus
High inherent strength
High melting point
Low electrical conductivity

Question 6

Material Characteristics for Ionic bonds (4, 3 examples)

Answer 6

High strength
High elastic modulus
High melting point
Poor electrical conductivity
Magnesia, Alumina and Cement

Question 7

Material Characteristics for Metallic bonds

Answer 7

High melting points
high boiling points
Electrical conductivity
Opaqueness
Malleability

Question 8

describe a ceramic and its bonding

Answer 8

inorganic non-metallic materials made from compounds of a metal and non-metal. the bonds are a mix of covalent and ionic

Question 9

Material characteristics of ceramics

Answer 9

Electrical and thermal insulators

Brittle

Question 10

What is an intramolecular force

Answer 10

the force which holds together the atoms making up the molecule or compound

Question 11

what are the relationships between r, r0 and F between atoms

Answer 11

r > 10r0 there is a very little F (gas)
r < 10r0 Attractive forces increase
r < r0 Repulsive forces dominate
r=r0 F = dU/dr = 0

Question 12

Seven properties that describe metals ceramics and polymers

Answer 12

1. Hardness
2. Resistance to corrosion
3. Elastic Modulus
4. Ductility
5. Wear Resistance
6. Conductivity
7. Density

Question 13

how many molecules per m^3 are there for solids. liquids and gases

Answer 13

10*28

1025

Question 14

Elastic modulus of metals ceramics and polymers

Answer 14

Ceramics >200GPa
Metals 20-200GPa
Polymers <10GPa

Question 15

Young Modulus

Answer 15

axial stiffness (shape volume)
easy to measure in a tensile test

Question 16

what is shear modulus?

Answer 16

torsional stiffness (shape)
relatively easy to measure in a torsion test

Question 17

What is Bulk Modulus?

Answer 17

Volumetric stiffness (volume)
difficult to measure because of very small volume changes

Question 18

Young Modulus

Answer 18

axial stiffness (shape volume)
easy to measure in a tensile test`

Question 19

What is the quantity of the area under the a stress strain graph?

Answer 19

resilience