BSL Chemistry Glossary - atom - definition
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Definition: An atom is a very small particle which we can't see at all – even under a strong microscope. Atoms are found everywhere. Let me tell you what is inside an atom. Small negatively charged particles called an electrons move round the centre of the atom. The centre of the atom is called the nucleus. The nucleus is made up of protons (positively charged particles) and neutrons (neutral particles).
reproduced by permission from Hodder