Mountains of the British Isles and the Caledonian Mountains of
Scandinavia have the same rock composition as the Appalachian
Mountains. What does this tell us about the story of the past geology of
this part of Earth?

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.  

hypostyle hall;