Group 1Oxford AQA IGCSE Chemistry: Revision notes
Section 1
What are the properties of Group 1 metals?
Group 1 of the periodic table contains the alkali metals: lithium, sodium, potassium, and others further down the group. They share these properties:
- Low density — the first three (lithium, sodium, potassium) are less dense than water and float on it
- Soft metals that can be cut with a knife
- Shiny when freshly cut, but tarnish quickly in air
Section 2
How do Group 1 metals react with non-metals?
Group 1 metals react with non-metal elements to form ionic compounds. Because Group 1 metals have one electron in their outer shell, they lose it to form an ion with a single positive charge (+1). The resulting ionic compounds are typically white solids that dissolve in water to form colourless solutions.
Sodium reacts with chlorine to form sodium chloride (NaCl), a white solid that dissolves in water to give a colourless solution.
Section 3
How do Group 1 metals react with water?
Group 1 metals react with water, releasing hydrogen gas and forming a metal hydroxide:
metal + water → metal hydroxide + hydrogen
For example: 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
The metal hydroxides formed (such as sodium hydroxide) dissolve in water to give alkaline solutions — this is why the group is called the alkali metals.
When describing the reaction of a Group 1 metal with water, mention all three observations expected: fizzing/effervescence (hydrogen gas), the metal moving/floating, and (for the more reactive metals) a flame or explosion.
Section 4
How does reactivity change down Group 1?
Reactivity increases going down Group 1. This means potassium is more reactive than sodium, which is more reactive than lithium. Going down the group, the outer electron is in a shell that is further from the nucleus and more easily lost, making the reaction with water or non-metals more vigorous.
Do not confuse the trend in Group 1 (reactivity increases down the group) with Group 7 (reactivity decreases down the group) — they go in opposite directions.
Must Know
- Group 1 = alkali metals: low density (first three float on water), soft, shiny when cut
- React with non-metals to form ionic compounds with metal ion charge +1
- These compounds are white solids that dissolve to give colourless solutions
- React with water to release hydrogen gas and form a metal hydroxide
- Metal hydroxides dissolve to give alkaline solutions
- Reactivity increases going down Group 1
That's the notes covered.
Carry on to the next subtopic.