Answer: The basic unit of matter
Explanation:
An atom is the smallest unit of an element or any matter that can ever exist and still retain the properties of that matter. So, since matter could exist as gases, liquids or solids - atoms serves as the basic unit of matter.
Furthermore, an atom is neither a positively charged nor a negatively charged particle rather it is neutral (with no charge).
As well, it is a cell that is regarded as the basic unit of all living things, not an atom
Thus, an atom is best described as the basic unit of matter whether living or non-living.
