Question

Sodium, potassium and lithium are stored under oil, give reason.

Answer 1

Hint: Sodium, potassium, and lithium can lose electrons easily. Sodium, potassium, and lithium can react easily with the gases present in the air or with the moisture. The oil prevents the reaction of alkali metals with air and moisture.

Complete step by step answer:
Sodium, potassium, and lithium all are alkali metals. All belong to the group-first. Metals tend to lose electrons. On going left to right in the periodic table the reactivity of the metals decreases. On going left to right in the periodic table the electronegativity increases, so it becomes difficult to remove electrons from the metals, so the reactivity decreases.
The alkali metals are present at the top left of the periodic table and the electronegativity of the alkali metals are least so, the alkali metals are most reactive.
Alkali metals are sensitive or we can say very reactive to the air and water. They are so reactive that the reaction is sometimes explosive. They are not found in elemental form in nature. They are found in the form of compounds. Alkali metal forms oxides in presence of oxygen.

Therefore, due to the high reactivity of alkali metals towards air and moisture, they are stored in kerosene oil.

Note:
Alkali metals are the most reactive metals of the periodic table. The reactive of alkali metals increases down in the group. Down in the group, the electronegativity decreases so, the metal loses electrons easily so, the reactivity of the metal increases. Among alkali metals, cesium is the most reactive.