Question

Answer the following question guys

Answer 1

a. We classify elements to make their study easier.
b. Chemical properties and atomic mass.
c. He left some gaps so that new elements which will be discovered in future could be easily placed in the table without disturbing it.
d. There was no mention about noble or inert gases because they were not been discovered at that time.
e. According to the modern periodic table, the 2 isotopes should be placed in the same slot because the modern periodic table is based on atomic number rather than atomic mass. And isotopes have same atomic number and different atomic mass.