PLEASE HELP QUICKLY!! You have performed a titration on a 15.00 mL sample of HCl. To reach the endpoint of the titration, you added 21.78 mL of 0.130 M NaOH. The products of this reaction are salt and water. What was the concentration (in M) of HCl in the sample?

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.