Describe the main features of Mendeleev’s periodic table?

Solution:
The main features of Mendeleev's Periodic Table are: 
1) The periodic table consists of vertical columns called groups, and horizontal rows called periods.
2)There are 7 periods and 8 groups.
3) All the groups are divided into subgroups.
   Some vacant spaces in the periodic table were left for undiscovered elements.
Vacant space below aluminium and germanium. which were named Eka- aluminium and Eka- silicon.
eka- aluminium was the element gallium. Similarly, germanium took the place of eka-silicon which is below silicon in the modern periodic table.