Science · Chemistry basics
Atoms & elements
The building blocks of matter.
What are atoms?
Everything around you is made of matter. Matter is anything that has mass and takes up space. Atoms are the tiniest building blocks of matter. They are so small you cannot see them with your eyes. Millions of atoms could fit on the full stop at the end of this sentence. All matter is made from different types of atoms joined together in different ways.
Elements: Pure substances made from one type of atom
An element is a pure substance made from only one type of atom. You cannot break an element down into simpler substances. Scientists have found about 118 different elements. Each element has its own special properties. For example, oxygen is a gas we breathe. Gold is a shiny metal. Carbon is found in pencil lead. Every element has a unique name and symbol.
The Periodic Table
The Periodic Table is a chart that organizes all the known elements. Each element has a one- or two-letter symbol. For example, O stands for oxygen, C for carbon, and Au for gold. The symbol Au comes from gold's Latin name. The Periodic Table groups elements with similar properties together. It helps scientists predict how elements will behave.
Atoms in everyday materials
Most materials are made from atoms of different elements joined together. Water contains hydrogen and oxygen atoms. Table salt contains sodium and chlorine atoms. Your body contains mostly carbon, hydrogen, oxygen, nitrogen, calcium and phosphorus atoms. When atoms join together they make molecules or compounds. Understanding atoms helps us understand why materials behave the way they do.
Worked examples
1. A piece of pure copper wire contains only copper atoms. Is copper an element or a compound?
- Check the definition: an element is made from only one type of atom.
- The copper wire contains only copper atoms, not a mixture of different atoms.
- Therefore, copper is an element.
2. Water has the symbol H₂O. Does this mean water is an element?
- Look at the symbol: H stands for hydrogen and O stands for oxygen.
- Water contains two different types of atoms joined together.
- An element contains only one type of atom, so water is not an element.
- Water is a compound because it contains different atoms joined together.
3. Iron has the symbol Fe. What does this tell us about iron?
- Iron has a single symbol (Fe) on the Periodic Table.
- This means iron is made from only one type of atom.
- Therefore, iron is an element.
- The symbol Fe comes from iron's Latin name, ferrum.
Try it yourself
Aluminium foil is made from pure aluminium with the symbol Al. Is aluminium an element? Explain your answer.
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