3. Metals + Reactivity
- A reactive metal wants to give up
its electrons to form ions with
stable outer electron shells
- Will form a new compound easily
- Sometimes we want more reaction,
but sometimes we want less
reaction
- We can combine or compare
metals to suit our purposes
6. What determines which metal will react?
- Based on experimentation and creating reactivity series
- Simply mix things together, heat them, or add other substances, and see what
is created
- Experience gained over centuries of work
- Only later, was the theory developed based on electron structure
7. 3. Metals with Carbon
No reaction. Therefore magnesium is more reactive than carbon
8. 3. Metals with Carbon
Reaction observed! Molten lead is formed and CO2 gas bubbles
away. Therefore, we conclude that carbon is more reactive than lead
9. 3. Metals with Carbon
- Carbon is more reactive than some metals
- It will reduce their oxides to form the metal
- It is called the reducing agent
12. 4. Metals with Metals (Competing for Oxygen)
- The tests confirm that iron, zinc and lead are all more reactive than copper
(same result as before)
- The iron acts as a reducing agent
- A metal will reduce the oxide of a less reactive metal
- This reaction is always exothermic
13. Application: Thermite
- Aluminium is more reactive than iron
- If we mix aluminium with iron oxide, what do you predict will happen?
14. 4. Metals with Solutions
- A metal will displace less reactive metals from a solution of its ions
15. Summary
- These are all redox reactions because electrons are moving between ions!
- The more reactive metal will want to form positive ions more readily
17. Extra terminology: Oxidation State
- A loss of negatively-charged electrons corresponds to an increase in oxidation number
- A gain of electrons corresponds to a decrease in oxidation number.
- Therefore, the element or ion that is oxidised undergoes an increase in oxidation number.
Oxidation number has increased
18. Applications of the Reactivity Series
Case Study: The sacrificial rust protection of iron
- Zinc is more reactive than iron
- We can coat iron with zinc to protect from rust
- The zinc will oxidise first, protecting the iron core from deterioration
