Ateam of scientists is studying the fossils in the cross-section of rock shown below. between which two layer of fossils can secondary succession be observed? a) layers 1 and 2. b) layers 2 and 3. c) layers 3 and 4. d) layers 1 and 4.

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.