1. What is the name given to group of three similar elements by Dobereiner?
2. Why was Dobereiner's system of classificiation of elements into triads not found to be useful?
3. State "Newlands law of Octaves" for classification of elements.
4. Name the fundamental property used by Mendeleev as the basis of classification.
5. How many groups and periods are there in the Modern periodic table?
6. What was the prediction of Mendeleev regarding the gaps in his periodic table?
7. How is valency of an element determined?
8. What will be the valency of an element having atomic number 15?
9. How does valency vary in going down a group?
10. Why inert gases have zero valency?
11. What would be the valency of an atom containing 8 electrons in its outermost shell?
12. How does the electronegative character of elements vary along a period of the periodic table?
13. The present classification of elements is based on which fundamental property of elements?
14. Among first ten elements in the modern periodic table name the metals present.
15. Metals are on which side of Modern periodic table?
16. Give reason why Silicon is classified as metalloid.
17. X and Y are two elements having similar properties which obey Newlands law of Octave. How many elements are there in between X and Y?
18. On what basis the position of Co and Ni were resolved in modern periodic table?
19. Name two elements, other than Gallium, whose existence was predicted by Mendeleev.
20. What is the atomic radius of hydrogen atom?
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