Reactions & Atomic Structure
Reactivity Series
Order of reactivity of metals
The reactivity series lists metals in order of how reactive they are. The most reactive metals are at the top, the least reactive at the bottom.
The Reactivity Series
Displacement Reactions
A more reactive metal displaces a less reactive metal
The Rule
A more reactive metal will displace a less reactive metal from its compound in solution.
More reactive metal + Compound of less reactive metal → Compound of more reactive metal + Less reactive metal
Reaction Happens
Zinc + Copper sulfate → Zinc sulfate + Copper
Zinc is MORE reactive than copper, so displaces it.
No Reaction
Copper + Zinc sulfate → No reaction
Copper is LESS reactive than zinc, cannot displace it.
Observation
When a displacement reaction occurs, you may see:
- • A colour change in the solution
- • A solid metal appearing (coating on the added metal or sinking to the bottom)
- • Bubbles if a gas is produced (when reacting with acid)
Extracting Metals
From ores to pure metals
Methods of Extraction
How a metal is extracted depends on its position in the reactivity series:
High Reactivity (K, Na, Ca, Mg, Al)
Electrolysis: Use electricity to break down the molten compound. Expensive but necessary.
Medium Reactivity (Zn, Fe)
Reduction with Carbon: Heat the ore with carbon (coke) in a blast furnace. Carbon removes oxygen from the metal oxide.
Low Reactivity (Cu, Ag, Au)
Found native: Gold is found as pure metal. Copper can be extracted by heating in air or by bacterial processes.
Rates of Reaction
How fast reactions happen
Measuring Rate
The rate of reaction measures how quickly reactants turn into products.
Rate = Amount of reactant used (or product formed) ÷ Time
Units: g/s or cm³/s or mol/s
Measuring: Volume of gas, mass loss, colour change
Collision Theory
For a reaction to happen, particles must:
1. COLLIDE: Particles must bump into each other
2. Have enough ENERGY: The activation energy
More successful collisions per second = Faster reaction
Factors Affecting Rate
Changing the speed of reactions
Temperature
Higher temperature = faster reaction
- • Particles move faster
- • More frequent collisions
- • Particles have more energy (more collisions exceed activation energy)
Concentration
Higher concentration = faster reaction
- • More particles in same volume
- • More frequent collisions
- • For gases: higher pressure has same effect
Surface Area
Larger surface area = faster reaction
- • Powder reacts faster than lumps
- • More particles exposed to react
- • More collisions possible at the surface
Catalysts
Catalysts speed up reactions without being used up
- • Lower activation energy needed
- • Not used up in the reaction
- • Can be reused many times
Atomic Structure
Inside the atom
Structure of the Atom
Protons
Positive charge (+1). Found in nucleus. Determine the element.
Neutrons
No charge. Found in nucleus. Give mass to the atom.
Electrons
Negative charge (-1). Orbit in shells. Involved in bonding.
Key Facts
Atomic Number: Number of protons (defines the element)
Mass Number: Protons + Neutrons
Atoms are neutral: Number of protons = Number of electrons
Electron shells: 1st holds 2, 2nd holds 8, 3rd holds 8
Periodic Table Structure
Groups and electronic structure
Groups and Periods
Groups (Columns)
Elements in the same group have the same number of electrons in their outer shell.
Example: Group 1 has 1 outer electron, Group 7 has 7 outer electrons.
Periods (Rows)
Elements in the same period have the same number of electron shells.
Period 1 has 1 shell, Period 2 has 2 shells, etc.
Electronic Configuration Examples
Sodium
Electrons: 2, 8, 1
Group 1, Period 3
Chlorine
Electrons: 2, 8, 7
Group 7, Period 3
Argon
Electrons: 2, 8, 8
Group 0, Period 3 (Noble gas)
Practice Questions
Test your understanding
Displacement [3 marks]
Iron is added to copper sulfate solution. A reaction occurs and a brown solid forms. Explain what happens, using the reactivity series.
Answer:
Iron is more reactive than copper. [1 mark]
Iron displaces copper from the copper sulfate solution. [1 mark]
The brown solid is copper metal. The equation is: Fe + CuSO₄ → FeSO₄ + Cu [1 mark]
Rates of Reaction [4 marks]
Explain, using collision theory, why increasing the temperature increases the rate of a reaction.
Answer:
At higher temperatures, particles have more kinetic energy and move faster. [1 mark]
This means there are more frequent collisions between particles. [1 mark]
More particles have energy greater than the activation energy. [1 mark]
Therefore there are more successful collisions per second, so the reaction is faster. [1 mark]
Atomic Structure [3 marks]
An atom has atomic number 11 and mass number 23.
a) How many protons does it have? [1 mark]
b) How many neutrons does it have? [1 mark]
c) What is its electronic configuration? [1 mark]
Answer:
a) Protons: 11 (atomic number = number of protons) [1 mark]
b) Neutrons: 23 - 11 = 12 neutrons [1 mark]
c) Electronic configuration: 2, 8, 1 (2 in first shell, 8 in second, 1 in third) [1 mark]
This is sodium (Na).
Extraction Methods [3 marks]
Aluminium is extracted by electrolysis but iron is extracted by reduction with carbon. Explain why different methods are used.
Answer:
Aluminium: High in the reactivity series, aluminium bonds very strongly to oxygen in its ore. Carbon cannot displace it, so electrolysis is needed. [1 mark]
Iron: Medium in the reactivity series, carbon (more reactive) can displace iron from its ore by removing oxygen. [1 mark]
Reason: The extraction method depends on the metal's position in the reactivity series - more reactive metals need more energy-intensive methods. [1 mark]
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