Which of the following is a characteristic of science? A It asks questions about the natural world.
B It asks questions that cannot be tested.
C It is done by only one scientist at a time.
D It uses opinions to make conclusions.

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.