atomic theory
noun/əˌtɒmɪk ˈθɪəri/
/əˌtɑːmɪk ˈθiːəri/, /əˌtɑːmɪk ˈθɪri/
[uncountable] (chemistry, physics)- the theory that all elements are made up of small particles called atoms, which are made up of a central nucleus surrounded by moving electrons
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atomic theory