When a scientific theory has been tested and proved by the scientific community, it becomes a law. true or false

False

Explanation:

Because laws and theories are developed for different purposes, laws never become theories, and theories do not become laws.  

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answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.