Group 1 — The Alkali MetalsAQA GCSE Chemistry: Revision notes

Section 1

Why are Group 1 elements grouped together?

The periodic table arranges elements in order of atomic (proton) number, so that elements with similar properties fall into the same column, or group.

Group 1, the alkali metals, includes lithium, sodium, potassium (and rubidium, caesium, francium further down). Their shared position in the periodic table reflects a shared feature of their atomic structure.

Key termsgroupatomic number

Section 2

Why do all Group 1 metals behave similarly?

Every alkali metal has just one electron in its outer shell. This single outer electron is easily lost, which is why the alkali metals:

Are all very reactive metals
Form ions with a +1 charge
React in similar ways with other substances

The position of an element in the periodic table is directly related to the arrangement of electrons in its atoms, and therefore to its atomic number.

Key termsouter electron

Think of it like this

Think of the single outer electron as something the atom is eager to hand off — the easier it is to give away, the more reactive the metal.

Section 3

How do alkali metals react with oxygen, chlorine and water?

With oxygen: alkali metals burn to form a white metal oxide, e.g. 4Li + O2 → 2Li2O
With chlorine: they react to form a white metal chloride salt, e.g. 2Na + Cl2 → 2NaCl
With water: they react vigorously, floating and moving across the surface, fizzing as hydrogen gas is produced, and forming a metal hydroxide solution, e.g. 2K + 2H2O → 2KOH + H2

Reactivity increases going down the group — potassium reacts more violently with water than sodium, which reacts more vigorously than lithium.

Key termsmetal hydroxide

Example

Sodium added to water fizzes, moves rapidly across the surface, may melt into a ball from the heat released, and eventually disappears as it fully reacts.

Common mistake

Don't say alkali metals react with water to make hydrogen oxide — the product is a metal hydroxide solution plus hydrogen gas.

Section 4

Why does reactivity increase down Group 1?

Going down the group, atoms get larger and the single outer electron is further from the positively charged nucleus, held less tightly, and shielded by more inner shells. This makes the outer electron easier to lose, so reactivity increases down the group.

This allows you to predict the likely reactivity and reactions of an alkali metal from its position in the periodic table, even one you have not studied directly.

Key termsreactivity trend

Must Know

Group 1 metals (alkali metals) all have one electron in their outer shell
They react with oxygen to form metal oxides, with chlorine to form metal chlorides, and with water to form a metal hydroxide plus hydrogen gas
Reactivity increases going down Group 1
The single outer electron is lost more easily further down the group, as it is further from the nucleus
Position in the periodic table reflects electron arrangement, which lets you predict reactivity

That's the notes covered.

Carry on to the next subtopic.