What Are Group 1 Elements?

Group 1 elements are known as the alkali metals. These elements are found in the first column of the periodic table.

Examples of Group 1 elements include:

• Lithium (Li)
• Sodium (Na)
• Potassium (K)
• Rubidium (Rb)
• Caesium (Cs)

These metals are called alkali metals because they react with water to form alkaline solutions.

Electronic Structure of Group 1 Elements

All Group 1 elements have one electron in their outer shell.

Example electron configurations:

• Lithium → 2,1
• Sodium → 2,8,1
• Potassium → 2,8,8,1

Because they have only one outer electron, these metals lose that electron easily during chemical reactions.

This forms positive ions with a +1 charge.

Example:

Na → Na⁺ + e⁻

Physical Properties of Alkali Metals

Group 1 metals share similar physical properties.

Soft Metals

Alkali metals are very soft compared to most other metals.

They can often be cut easily with a knife.

Example:

Sodium can be cut easily due to its softness.

Low Density

Group 1 metals have low densities.

Some of them are less dense than water, meaning they float.

Example:

Sodium floats on water.

Low Melting Points

Compared with other metals, alkali metals have relatively low melting points.

Their melting points decrease down the group.

Chemical Properties of Group 1 Metals

Group 1 metals are very reactive.

Their reactivity increases as you move down the group.

Reaction with Water

Alkali metals react vigorously with water to produce:

• Metal hydroxide
• Hydrogen gas

Example reaction:

2Na + 2H₂O → 2NaOH + H₂

This reaction produces sodium hydroxide and hydrogen gas.

Reaction with Oxygen

Group 1 metals react with oxygen to form metal oxides.

Example:

4Na + O₂ → 2Na₂O

These reactions occur quickly in air.

Reaction with Halogens

Alkali metals react with halogens (Group 7 elements) to form ionic salts.

Example:

2Na + Cl₂ → 2NaCl

This reaction produces sodium chloride.

Trend in Reactivity Down the Group

Reactivity increases down Group 1 because:

• Atoms become larger
• The outer electron is farther from the nucleus
• The outer electron is lost more easily

This makes metals like potassium more reactive than sodium.

Uses of Group 1 Metals

Although they are very reactive, alkali metals have several uses.

Examples include:

• Lithium batteries used in electronic devices
• Sodium lamps used in street lighting
• Potassium compounds used in fertilisers

These applications are important in technology and agriculture.

Exam Tip (5070)

Students are often asked to:

• Describe physical properties of Group 1 metals
• Explain reactivity trends down the group
• Write equations for reactions with water

Example exam question:

Why does reactivity increase down Group 1?

Answer:

Reactivity increases because the outer electron is farther from the nucleus and is lost more easily.

Practice Question

What gas is produced when sodium reacts with water?

Answer

The gas produced is hydrogen (H₂).

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