Answer:
Magnesium and calcium belong to the second group i. e. alkaline earth metals. They are known as earth metals because they are extracted from the earth. They are very reactive elements. Their reactivity increases when we go from top to bottom because the outermost electrons goes farther from the nucleus i. e. atomic radius increases so less energy is needed for its removal.
Answer:
Explanation:
(NH4)2SO4+Pb(NO3)2...............PbSO4+2NH4NO3
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Answer:

Explanation:
Combination reactions are the reactions in which two or more atoms/ molecules combine to give a single product.
Aluminum metal combines with iodine to given aluminium iodide.
Aluminium has a valency of 3 and iodine has valency of 1, so the formula is 
The reaction is shown below as:

Answer:
Stannic fluoride, SnF4
Explanation:
The chemical formula of Barium nitride is Ba(NO3)2.
The chemical formula of Cobaltous chloride is COCl2.
The chemical formula of Sodium Oxide is Na2O.
So the correct one is stannic fluoride, SnF4.