Question

Differences between Morden periodic table and Mendeleev's periodic table

Answer 1

modern periodic table:
#18 groups and 7 period
#element are grouped in the increasing order of atomic number
#noble gases are placed in 18 group
#seperate groups for transmission elements and inner transmission elements
Mendeleev's periodic table:
#8 groups and 6 periods
#elemnts grouped in the increasing order of atomic mass
#noble gases are placed in separate group of 0.
# no separate group for transition and inner transition elements

Answer 2

The major difference is that the elements in Mendeleev's periodic table were arranged by atomic mass and the modern periodic table arranges elements by atomic number. Of course as elements are constantly being discovered there were significantly fewer elements in Mendeleev's periodic table.