Summary
Group I metals, known as alkali metals, are soft, have low melting points, and react vigorously with water, increasing in reactivity down the group. Halogens in Group VII are diatomic non-metals that become less reactive down the group, with a trend in color and physical state. More reactive halogens can displace less reactive ones from their halide compounds.
- Alkali Metals — soft metals with low melting points and densities, reacting vigorously with water. Example: Lithium, sodium, and potassium.
- Halogens — diatomic non-metals showing a trend in color and reactivity. Example: Chlorine is a greenish-yellow gas, bromine is a reddish-brown liquid, and iodine is a dark grey solid.
- Displacement Reactions — more reactive halogens displace less reactive ones from halide compounds. Example: Chlorine can displace bromine and iodine from their halide compounds.
Exam Tips
Key Definitions to Remember
- Alkali Metals: Soft metals with low melting points and densities.
- Halogens: Diatomic non-metals with trends in color and reactivity.
- Displacement Reaction: A more reactive halogen displaces a less reactive one from its halide compound.
Common Confusions
- Confusing the reactivity trends of alkali metals and halogens.
- Misunderstanding the states of halogens at room temperature.
Typical Exam Questions
- What happens when sodium reacts with water? It forms sodium hydroxide and hydrogen gas.
- Which halogen can displace bromine from sodium bromide? Chlorine can displace bromine.
- Describe the trend in reactivity of Group I metals. Reactivity increases down the group.
What Examiners Usually Test
- Trends in physical and chemical properties of Group I and VII elements.
- Ability to predict reactions based on group trends.
- Understanding of displacement reactions among halogens.