Atom
/ˈætəm/
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Definition
(noun) The smallest possible amount of matter which still retains its identity as a chemical element, now known to consist of a nucleus surrounded by electrons.
Sentence Examples
A water molecule has two hydrogen atoms and one oxygen atom.
The universe is a gigantic atom and everything is affected by it.
CEFR Practice Quiz
An ____ is the smallest unit of a basic chemical element from nature.