Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).

$(i)$ Write the electron-dot structures for sodium,oxygen,and magnesium.
$(ii)$ Show the formation of $Na_{2}O$ and $MgO$ by the transfer of electrons.
$(iii)$ What are the ions present in these compounds?

Which of the following methods is suitable for preventing an iron frying pan from rusting?

Which of the following pairs will give displacement reactions?

Write equations for the reactions of:
$(i)$ Iron with steam
$(ii)$ Calcium and potassium with water

Samples of four metals $A$,$B$,$C$ and $D$ were taken and added to the following solutions one by one. The results obtained have been tabulated as follows.

Metal	Iron $(II)$ sulphate	Copper $(II)$ sulphate	Zinc sulphate	Silver nitrate
$A$	No reaction	Displacement	No reaction	Displacement
$B$	Displacement	Displacement	No reaction	Displacement
$C$	No reaction	No reaction	No reaction	Displacement
$D$	No reaction	No reaction	No reaction	No reaction

Use the table above to answer the following questions about metals $A$,$B$,$C$ and $D$:
$(i)$ Which is the most reactive metal?
$(ii)$ What would you observe if $B$ is added to a solution of Copper $(II)$ sulphate?
$(iii)$ Arrange the metals $A$,$B$,$C$ and $D$ in the order of decreasing reactivity.