When a wave moves, what happens to the medium? a it moves forward with the wave b it moves only perpendicular to the energy of the wave c it moves up and down or back and forth, but it does not move forward with the wave d it moves only parallel to the energy wave

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.