Chapter 1: Let us answer these: (Page-6)

Q1. What was Mendeleev's principle for the classification of elements?

Ans:   1) Mendeleev's table was based on mass number.

          2) He arranged the elements on the basis of their properties in increasing order of their atomic mass.

Q2. Using Mendeleev's Pertiodic Table, Perdict the formula for the oxides of the following elements:  k, Cl, Al, Si, Ba.

Ans:
   

Q3. Besides gallium, which other elements have since been discovered that were left by Mendeleev in his Periodic Table? 

Ans:   Besides gallium, germanium and scandium have been discovered.

Q4. Give your Reason why the noble gases are placed in a separate group.

Ans: Noble gases are inactive, do not resemble other elements and all of them show same properties, hence they are grouped separately.

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