You are given samples of three metals : Sodium, magnesium and copper. Suggest any two activities to arrange them in order to their decreasing reactivity.

Explanation

(i) Different metals react with oxygen at different rates. E.g., Sodium (Na) and potassium (K) catch fire, if left in open. Hence, these are the most reactive metals. To prevent accidental fires, these metals are kept immersed in kerosene oil. Magnesium burns in air only by heating. So, it is less reactive than sodium and potassium. Copper (Cu) does not burn on heating but blister copper burns. Hence the order of reactivity of these metals with oxygen is :
`Na gt Mg gt Cu`.
(ii) Metals react with water to produce a metal oxide and hydrogen gas. Sodium (Na) and potassium (K) react violently with cold water. So the reaction is violent and exothermic. Magnesium (mg) does not react with cold water. It reacts with hot water. Metals like lead, copper, silver do not react with water at all. The reactivity series of metals towards water is :
`Na gt Mg gt Cu`.