Neutron moderation is used to counteract: A. the low concentration of uranium-235 in nature.

B. the heat generated during nuclear fission reactions.

C. the chain reactions that naturally occur with uranium-235.

D. the minimal chance that the newly formed neutrons of a fission

reaction are absorbed by more atoms.

e

explanation:

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.