Lecture 4: Metals

Question 1

1. What is an atomic orbital? And what is a molecular orbital?

Answer 1

can be used to represent the regions in a molecule where an electron occupying that orbital is likely to be found. (The probability density function).

Question 2

2. When atomic orbitals are combined, two molecular orbitals are created. How do the energies compare and for a chemical bond, where would you expect to find the electrons?

Answer 2

HOMO and LUMO.
The energy difference is the HOMO-LUMO gap. The difference in energy between these two frontier orbitals can be used to predict the strength and stability of transition metal complexes.

Question 3

3. For the creation of molecular bonds, what is the difference between ionic compounds, molecular compounds and metallic materials?

Answer 3

ionic compounds -

Question 4

4. Why is the conduction band on metals overlapping with the valence band?

Answer 4

because the electrons can jump between different atoms and orbitals which allows it to be a conductor. All the atoms in the metal can easily lose their outer electrons. So you start to have a sea of electrons. The anti-bonding and bonding have the same energy, no bandwidth of energy. The orbitals are close in energy for all atoms.

Question 5

5. Based on the electron sea model, why can metals easily produce alloys?

Answer 5

You can substitute atoms by different ones. Because they have no set bonds with each other.

Question 6

6. What is a redox reaction?

Answer 6

Because both reduction and oxidation are going on side-by-side, this is known as a redox reaction. It involves a transfer of electrons between two species

Question 7

7. Describe the three main methods to avoid oxidation based on redox reactions.

Answer 7

How do you avoid corrosion?
Noble - Cover with paint, do not have access to oxygen but if you have a scratch, it will have access to oxygen.
2. Sacrificial - You make in contact, one metal that oxidises more easily than the material you are covering.
3. Alloy

Question 8

8. Mention 2 metals commonly used in implants and describe what you would expect to be the chemical surface of these metals.

Answer 8

Stainless Steel
Cobalt chromium
Titanium alloys - Carboxylic/silanes

Question 9

9. How can you tell if an implant is well integrated to bone? What would you look for and why?

Answer 9

1. Look at microscope of haversian canals of boundaries between bone and implant.
   You look at:
   collagen. The dark blue is the fibrous tissue. The creation of a new material between the bone and the implant show that its a bad integration.