In what areas of the periodic table do you find the least reactive elements?

Noble gases are nonreactive, nonmetallic elements in group 18 of the periodic table. Noble gases are the least reactive of all elements. That's because they have eight valence electrons, which fill their outer energy level.

Elements: Argon

it's c (engineer's do their work with mechanical stuff not on any living being)

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.