These 3 questions, plz??:

6. Define valency. Classify the following cations on the basis of their valences : Ca++,Cu++, NH4+. Al+++

7. What were the conclusions of Rutherford's  α -particle scattering experiment.

8. Calculate the molar mass of the following substance and identify the polyatomic ions present in each of them. 
(a) Al2(SO4)3            (b) CaCO3

[Given that atomic mass of Al=27 u, S=32 u, O=16  i. Ca=40  u.

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