a) explain why atomic number is more important than atomic weight in determining chemical properties?
b) compare the arrangement of elements in mendeleev's periodic table and modern periodic table
Chemical properties of elements are functions of their atomic numbers. The reason is that atomic number decides the number of electrons in valence shell of elements which directly determine the chemical properties of elements.
Elements in mandaleev's periodic table are arranged in increasing order of their masses. Thus as per mandaleev, the chemical properties of elements are functions of their masses. Thus there arrangement is different from those in modern periodic table which has elements arranged as per modern atomc law as stated in the first line.