Lesson 1 of 5
Atoms and elements
Goal: Describe atoms and elements using Dalton’s model.
Everything is made of tiny particles called atoms. An element is a substance made of only one type of atom.
Dalton’s model
- Atoms are like tiny solid balls. About 200 years ago, John Dalton said that all matter is made of atoms, and that an atom cannot be broken down into anything simpler.
- All the atoms of one element are identical. Every gold atom is the same as every other gold atom.
- Atoms of different elements are different. A gold atom is not the same as a copper atom.
There are 118 elements. Scientists now know that atoms have even smaller parts inside them, but Dalton’s model is still a good way to picture elements and compounds.
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Key words in this lesson
Atom The smallest particle of an element that can exist
Element A substance made of only one type of atom
Compound Two or more elements chemically joined together
Dalton’s model The idea that atoms are tiny solid balls that cannot be broken down