Question

A soft metal stored under kerosene is :
A. sodium $\left( \text{Na} \right)$
B. calcium $\left( \text{Ca} \right)$
C. lithium $\left( \text{Li} \right)$
D. magnesium $\left( \text{Mg} \right)$

Answer 1

Hint: Metals are generally hard in nature due to their strong metallic bonding. There are few exceptions in metals which are soft. Softness is the intrinsic property of any metal. Any substance which is not kept in open air at room temperature is due to its high reactive nature. Check which is highly reactive and is a soft metal among all.

Complete step by step answer:
Let us discuss the options one-by-one and their properties:
A. sodium $\left( \text{Na} \right)$: Sodium element is present in group 1 due to presence of one valence electron. It has a large atomic size, because of all these reasons sodium metal is a soft metal. Moreover, the metallic bonding in sodium is not strong, hence it can be easily cut. Sodium due to its high reactive nature is not kept in open air. It easily catches fire on reaction with air and water.

B. calcium $\left( \text{Ca} \right)$: Calcium element is present in group 2 due to presence of two valence electrons. It has a large atomic size, because of all these reasons calcium metal is a soft metal. It is not very soft metal and can be cut with a knife with effort. Calcium is not so reactive in nature, so it is not stored under kerosene.

C. lithium $\left( \text{Li} \right)$: Lithium is not stored in kerosene because it is the lightest metal among all metals. It floats on its surface and reacts with air. Instead of kerosene, it is wrapped in paraffin wax and stored. Lithium is a soft metal, so soft that it can be even cut by knife.

D. magnesium $\left( \text{Mg} \right)$: Magnesium is also a soft metal which tarnishes in air. It is lustrous and silvery-white in colour. It is not stored under kerosene. This is because magnesium is not very reactive in nature.
A soft metal stored under kerosene is sodium $\left( \text{Na} \right)$
So, the correct answer is “Option A”.

Additional Information: Uses of sodium:
(1) Sodium vapours are used in streetlights and produce a bright yellow light.
(2) Liquid sodium is used as a coolant for nuclear reactors.

Note: The reason why sodium is placed under kerosene only is kerosene contains hydrocarbon chains of six to sixteen carbon atoms in length and sodium does not react with hydrocarbons. So, it is safe to keep sodium in organic substances.