3.5 The elements of Group 1

Summary: Figure 1 shows an electric car. It gets its power from a lithium battery. Lithium is an element in Group 1, on the left of the Periodic Table. Tags: science oxford-science student-book-7 chemistry Created: 2026-05-19 Last Updated: 2026-05-19

After this topic, you will be able to:

• describe the physical properties of the Group 1 Elements
• use data from tables or bar charts to describe patterns in the melting and boiling points of the Group 1 elements
• use patterns to predict reactions of the Group 1 elements with water.

Think back

1. State whether the elements on the left of the Periodic Table are metals or non-metals.
2. List three physical properties of a typical metal.
3. Give one chemical property of a typical metal.

Key idea Group 1 elements are very reactive. They easily take part in Chemical Reactions.

Key words Group 1, reactive

Figure 1 shows an electric car. It gets its power from a lithium battery. Lithium is an element in Group 1, on the left of the Periodic Table.

Figure 1An electric car.

Figure 2 shows the position of Group 1 in the Periodic Table. The Group 1 elements are also called the alkali metals.

Figure 2Group 1 is on the far left of the Periodic Table.

Figure 3Densities of Group 1 elements. Full text alternative to the content

Are Group 1 elements like other metals?

In many ways, the Group 1 elements are like other metals.

• They are good conductors of electricity and thermal Energy (heat).
• They are shiny when newly cut.

In some ways, Group 1 elements are different to other metals. Table 1 shows that Group 1 elements have lower melting points than typical metals, such as copper and platinum. The Group 1 elements are also softer than most other metals, and have lower densities. Table 1 Melting points of Group 1 elements and other metals. Element

Is the element in Group 1?

Melting point in °C

lithium

yes

180

sodium

yes

98

potassium

yes

64

rubidium

yes

39

copper

no

1083

platinum

no

1796

A Describe one difference between Group 1 elements and other metal elements.

Are there patterns in Group 1 properties?

The Group 1 elements show patterns in their physical and chemical properties.

The data in the first four rows of Table 1 show that melting point decreases from top to bottom of Group 1. The data in Table 2 show that boiling point also decreases from top to bottom of the group. Table 2 Boiling points of Group 1 elements. Element

Boiling point in °C

lithium

1330

sodium

890

potassium

774

rubidium

688

B Describe the pattern in boiling points from top to bottom of Group 1.

The Group 1 elements are very reactive. This means that they easily take part in chemical reactions. The Group 1 elements have exciting chemical reactions with water. The reactions make hydrogen gas and an alkaline solution. For example:

There is a pattern in the reactions. They all make hydrogen gas. Figures 4 and 5 show that the reactions get more vigorous (strong) from top to bottom of Group 1.

Figure 4Lithium, at the top of Group 1, reacts vigorously with water.

Figure 5The reaction of potassium with water is very vigorous.

C Predict the gas product in the reaction of rubidium with water.

Working scientifically The bar chart in Figure 3 shows densities of Group 1 elements. Describe the pattern.

Stretch zone

1. Copy and complete the sentences. The Group 1 elements conduct/do not conduct electricity. They have high/low densities. The Group 1 elements are softer/harder than most other metals.
2. Table 3 gives hardness values for some Group 1 elements. The bigger the value, the harder the element. Table 3Element Mohs hardness lithium 0.6 sodium 0.5 potassium rubidium 0.3 caesium 0.2 Plot the hardness values on a bar chart.Describe the pattern in hardness.Predict the hardness of potassium. Explain your prediction.

Stretch zone

1. Predict the gas product of the reaction of caesium with water. Give reasons for your answer.