A 25.0 mL sample of 0.723 M HClO4 is titrated with a 0.273 M KOH solution. The H concentration after the addition of 10.0 mL of KOH is M. 0.723 0.440 0.943 0.273 1.00x10-7

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.