2.2 Atoms
Summary: Look at Figures 1 and 2. What do you think they show? 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:
- define an atom
- define an element in terms of its Atoms.
Think back
- What is an element?
- What are particles?
- How are the particles arranged in a substance in the solid state?
Key idea An atom is the smallest particle of an element that can exist. The properties of an element depend on what its atoms are like and how they are arranged.
Key words atom, element
Look at Figures 1 and 2**. What do you think they show?**
Figure 1
Both pictures show the element silicon. Figure 1 was taken with a normal camera. Figure 2 was taken with a special type of microscope. It shows the surface of a silicon crystal at a magnification of ×10 000 000 (10 million).
Figure 2
Silicon is an important element. It holds the tiny electric circuits in every computer, tablet, and phone.
What are atoms?
The circles in Figure 2 are atoms. Atoms are particles. An atom is the smallest part of an element that can exist.
Every element is made up of just one type of atom. All the atoms of an element are the same as each other. The atoms of one element are different from the atoms of all other Elements. There are about 100 elements, so there are about 100 types of atom.
You can now give a better definition of an element: a substance that cannot be broken down into other substances. It contains just one type of atom.
A Give the number of types of atom in a piece of silicon.
All silicon atoms are the same. But silicon atoms are different from gold atoms. For example, gold atoms are bigger.
Gold atoms are also heavier than silicon atoms. This difference explains the data in Table 1. Table 1 The masses of gold and silicon.
B Describe two differences between gold and silicon atoms.
Just one atom?
One atom on its own does not have the properties of its element. A gold atom is not yellow. It is not shiny. It is not in the solid, liquid, or gas state.
The properties of an element are the properties of many atoms joined together, like those in Figure 3. The block of gold in Figure 4 has a mass of 1000 g. It is made up of about 3 000 000 000 000 000 000 000 000 atoms. Together, these atoms make the gold yellow and shiny.
Figure 3The circles represent a few atoms in solid gold. One atom on its own has no colour.
Figure 4When many gold atoms are arranged into a block of gold, the resulting substance has properties, like colour.
In a gold block, the atoms are touching each other in rows. They vibrate (shake) on the spot. The gold in Figure 4 is in the solid state. If you heat gold to 1064 °C, its atoms start moving around. The gold is melting. One atom of gold cannot melt. Only a group of many atoms can melt.
C Describe two differences between a gold atom and a block of gold.
Maths skills There are 3 000 000 000 000 000 000 000 000 atoms in a 1000 g gold bar. A gold ring has a mass of 10 g. Calculate the number of atoms in the ring.
Stretch zone
- Copy and complete the sentences. The smallest part of an element that can exist is called an atom/elemental. All the atoms of an element are different/identical. The atoms of one element are different/identical to the atoms of all other elements. An atom on its own does not have the properties of the element/elemental.
- An Olympic bronze medal is made up of three elements: copper, zinc, and tin. Give the number of types of atom in the medal. Explain your answer.
Stretch zone
- A student says that a gold atom is yellow and shiny, and that it is in the solid state at 20 °C. Explain why the student is incorrect.