Bonding and Properties

Question 1

What are the factors which control the properties of materials?

Answer 1

• Composition - what it is made from
• Bonding
• Crystal structure - arrangement of atoms
• Temperature
• Pressure

Question 2

Bonding controls:

Answer 2

• Melting temperature
• Density
• Thermal and Electrical Conductivity
• Coefficient of Thermal Expansion
• Stiffness

Question 3

What are the types of bonds?

Answer 3

Primary Bonds
- Ionic Bonds
- Covalent Bonds
- Metallic Bonds
Secondary Bonds
- Van der Waals Bonds
- Hydrogen Bonds

Question 4

Describe the mechanics of an ionic bond:

Answer 4

Valence electrons are transferred between atoms, creating ions with net charge. This charge difference creates an electrostatic attraction -> bond.

Question 5

Describe the mechanics of an covalent bond:

Answer 5

Bonding due to the sharing of electron orbitals. This creates directional structures.

Question 6

Describe the mechanics of an metallic bond:

Answer 6

Metal ions are sharing a sea of electrons. The bond is between the conduction electrons and the metal ions.

Question 7

Describe the mechanics of an hydrogen bond:

Answer 7

Intermolecular attraction of polarized molecules with hydrogen.

Question 8

Describe the mechanics of the Van der Waals bond:

Answer 8

Intermolecular attraction due to temporary, induced polarity on atoms.

Question 9

What are the presence of bonds among Metals?

Answer 9

Covalent + Metallic

Question 10

What are the presence of bonds among Polymers?

Answer 10

Covalent + Van der Waals

Question 11

What are the presence of bonds among Composites?

Answer 11

Covalent

Question 12

What are the presence of bonds among Ceramics?

Answer 12

Ionic + Covalent

Question 13

Rank the bonds according to bond energy:

Answer 13

Primary > Secondary

Ionic > Covalent, Metallic > Van der Waals, Hydrogen

Question 14

What is the relationship between thermal expansion coefficient and bond energy?

Answer 14

It decreases with increasing bond energy. It depends on the shape of the bond energy diagram. As temperature increases, the particle gains more energy, so is held less tightly against it’s bond atom, and thus is ‘expanding’.

Question 15

What is the relationship between melting temperature and bond energy?

Answer 15

Materials with higher bonding energy have higher melt temperatures, and thus, lower thermal expansion coefficients.,