In the following reaction, select which direction the reaction would shift towards if the temperature increased:
PCI;(g) + Heat <> PC13(g) + Cl2(g)
O a
towards the reactants
Ob
towards the products

no shift will occur
Oc

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.