CLASS - XI CHEMISTRY (Classification of Elements and Periodicity in Properties) work sheet -1

Topic: - Genesis of Periodic classification

1. How many elements are known at present?
2. Who was the first scientist to classify elements according to their properties?
3. What is the basis of triad formation of elements?
4. Stale the modern ‘Periodic law’?
5. Define and state Mendeleev’s periodic law.
6. How did Mendeleev arrange the elements?
7. Name the two elements whose existence and properties were predicted by
Mendeleev though they did not exist then.
8. Describe the main features of Mendeleev’s periodic table?