Here's why:
* High reactivity: Alkali metals (like lithium, sodium, potassium, rubidium, cesium, and francium) are extremely reactive. They readily react with water, oxygen, and even the moisture in the air.
* Danger of fire and explosions: These reactions can be violent, generating heat and even igniting the metal.
* Protection under oil: To prevent these dangerous reactions, alkali metals are stored under oil, usually mineral oil, which acts as a barrier to air and moisture.
Example: Sodium is a common alkali metal and is often stored under kerosene or mineral oil.
