A sample of aluminum chloride (AlCl3) has a mass of 37.2 g. Required:
a. How many aluminum ions are present?
b. How many chloride ions are present?
c. What is the mass in grams of one formula unit of aluminum chloride?

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.