When alkali metals react with water, they do so very vigorously. Here’s a simple explanation without using any equations:
- Observation: The metal floats on water and starts moving around on the surface. Tiny bubbles appear as a gas is released. The reaction produces heat, and in some cases, the gas may catch fire.
- Result: The reaction forms a strong alkaline solution in the water.
- Trend: The reactivity increases as you go down the group. Lithium reacts gently, sodium reacts faster, potassium reacts very vigorously, and rubidium and cesium can react explosively.
- Reason: Alkali metals have a single electron in their outer shell that is very easy to lose. Losing this electron releases energy, which makes the reaction hot and sometimes causes the gas to ignite.
This explains why alkali metals must be handled carefully around water.