A solution that is 0.024 M in Na+ can be prepared by adding how many grams of Na2SO4 (MW 142 g) to water and diluting to a final
volume of 140.0 mL?
1. 0.00024 g
2. 0.24 g
3. 95 g
4. 0.48 g
5. 0.0095 g

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.