Page 67 - Science Coursebook

4.3 Trends in Group 1

The structure of the Group 1 elements
Lithium has an atomic number of 3 and a mass number of 7. This atom contains
three protons, 3 electrons and 4 neutrons. The electrons are arranged as 2,1. This
arrangement of electrons is known as the electronic structure.

Sodium has an atomic number of 11 and a mass number of 23. This atom contains
11 protons, 11 electrons and 12 neutrons. The electrons are arranged as 2,8,1.
Potassium has an atomic number of 19 and a mass number of 39.
This atom contains 19 protons, 19 electrons and 20 neutrons.
The electrons are arranged as 2,8,8,1.

19p 20n
11p 12n
3p 4n

Lithium atom. Sodium atom. Potassium atom.

Questions
5 What happens to the size of the atoms as you go down this group?
A+I 6 What similarity is there in the structure of these atoms? (Hint: look at the
electron shell arrangements.)
A+I 7 Suggest why this group of metals is called Group 1.
A+I 8 What are the trends in the structure and behaviour of these elements in
Group 1?

Summary
• The elements in Group 1 share some properties.
• The trend in Group 1 is that the melting points and the boiling points
decrease, as you go down the group.
• The elements in Group 1 react more vigorously with water as you go
down the group.

4 Material properties 65