Samples of groundwater were collected and analyzed using absorption spectrophotometry. The samples contained 100 ppm of Calcium and 80 ppm of Magnesium to give the total hardness of calcium carbonate. Express the total hardness of CaCO3 in parts per million.

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.