Which of the following metals is the most reactive?

Give reasons for the following:
$(i)$ Metals conduct electricity.
$(ii)$ Non-metals in general do not displace hydrogen from dilute acids.
$(iii)$ Aluminium easily combines with oxygen but still it can be used for making kitchen utensils.

$(a)$ Show the formation of $MgO$ by the transfer of electrons.
$(b)$ Name the cation and anion.
$(c)$ Write three properties of ionic compounds.

What happens when calcium is treated with water?

Silver articles become black on prolonged exposure to air. This is due to the formation of

$(a)$ $A$ substance $X$,an oxide of a metal,is used extensively in the cement industry. This element is found in our bones also. On treatment with water,it forms a solution which turns red litmus blue. Identify $X$ and also write the chemical reaction involved.
$(b)$ Choose a metal from the following metals which reacts only with hot water: Sodium,magnesium,iron. Mention the products formed during the reaction.