The Modern Periodic Table

Question 1

Summarise the differences between the modern periodic table and Mendeleev’s periodic table (4)

Answer 1

1. In the MPT, the elements are arranged in order of increasing atomic number.
   In Mendeleev’s, the elements are in order of increasing atomic weight (relative atomic mass).
2. There are more elements in the MPT (over 100 elements). When Mendeleev constructed his table some elements hadn’t been discovered. (only 60 elements approx.)
3. There are no gaps in the MPT. Mendeleev’s contained gaps for undiscovered elements.
4. In the MPT, the transition elements are listed in a separate block in the middle of the table.
   Mendeleev didn’t put these elements in a separate block. He included them with the other elements.