How many milliliters of calcium with a density of 1.55 g/mL are needed to produce 12.4 g of hydrogen gas in the single replacement reaction below be sure to show the work that you did to solve the problem and balanced equation Ca + HF -> CaF2 + H2

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.