AQA GCSE Chemistry
AQA GCSE Chemistry
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Topic 1: Atomic structure and the periodic table
Topic 1: Atomic structure and the periodic table
Group 1
Group 1
The elements in Group 1 of the periodic table are called the alkali metals. These include lithium, sodium, potassium, rubidium, cesium, and francium. The alkali metals share characteristic properties because they each have a single electron in their outer shell, which makes them highly reactive.
Properties of alkali metals
Properties of alkali metals
Alkali metals have low density and are generally soft metals that can be cut with a knife.
As you move down Group 1:
Reactivity increases. This is because the single electron in the outer shell is further from the nucleus and easier to lose. For example:
Lithium is less reactive than sodium
Potassium is more reactive than both.
Melting and boiling points decrease, while their relative atomic mass increases.
Reactions
Reactions
1. Reaction with Water:
When alkali metals react with water, they form a metal hydroxide and hydrogen gas. The reactions become more vigorous as you move down the group.
For example, lithium reacts calmly, but sodium reacts more vigorously, and potassium may even ignite with a flame.
Reaction example:
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2 (g)
sodium + water → sodium hydroxide + hydrogen
2. Reaction with Oxygen:
Alkali metals also react with oxygen to form metal oxides. The speed of this reaction increases as you go down the group.
For example, sodium forms sodium oxide, while potassium can form potassium peroxide or potassium superoxide.
3. Reaction with Chlorine:
When alkali metals react with chlorine, they form white crystalline salts such as sodium chloride. The reactivity with chlorine increases down the group, with potassium reacting more vigorously than sodium.
Reaction example:
2Na(s) + Cl2 (g) → 2NaCl(s)
sodium + chlorine → sodium chloride
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