For a general reaction 2A + B >2C+D, the rate of forward reaction will be equal to: A. Kf[A][B]
B. Kf[2A][B]
C. Kf[A]^2[B]
D. Kf[A]^2+[B]​

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.