1Everything is made of atoms
Zoom into anything and you reach atoms: tiny particles, far too small to see. This gold bar is billions of billions of gold atoms.
atom
Lesson 5.1 notes
Atoms and elements
Everything is made of atoms. An element has only one kind of atom, and each element has a symbol.
2Dalton's model
In 1803 John Dalton said atoms are tiny solid spheres. They can't be split, made or destroyed.
Daltonmodel
3Each element has its own atoms
All the atoms of one element are the same. Atoms of different elements are different: one oxygen atom has the mass of 16 hydrogen atoms.
mass
4Elements
An element has only one kind of atom. Its atoms can be single, joined in molecules like O₂, or packed in a solid.
elementmolecule
5Chemical symbols
Every element has a symbol: a capital letter, sometimes followed by a small letter. Some come from Latin names.
symbol
6118 elements
The periodic table lists all 118 elements. More than three-quarters of them are metals.
periodic tablemetalnon-metal
Explore: Element explorer
Choose an element to see what its atoms look like.
Common mistake: CO is not the same as Co
CO is carbon monoxide: a carbon atom joined to an oxygen atom. Co is the element cobalt. Each capital letter starts a new symbol.
Remember
- Everything is made of atoms. Dalton pictured them as tiny solid spheres.
- An element has only one kind of atom. There are 118 elements.
- Each element has a symbol: a capital letter, sometimes followed by a small letter.
Going further at GCSE
GCSE: Atoms, elements and compounds → GCSE: Development of the atomic model →