How do alkali metals react with water?

Alkali metals react with water to produce hydrogen gas and alkali metal hydroxides, which are basic in nature.

Alkali metals, found in Group 1 of the Periodic Table, are known for their highly reactive nature, especially with water. This is due to their single electron in the outermost shell, which they are eager to lose in order to achieve a stable electron configuration. When an alkali metal comes into contact with water, a displacement reaction occurs. This means the metal displaces the hydrogen in the water, forming a metal hydroxide and releasing hydrogen gas.

For example, if you were to drop a small piece of sodium (Na) into water, the reaction would be as follows: 2Na(s) + 2H2O(l) -> 2NaOH(aq) + H2(g). This equation tells us that sodium reacts with water to form sodium hydroxide and hydrogen gas. The '(s)' after sodium indicates it is in a solid state, '(l)' after water denotes it is a liquid, '(aq)' after sodium hydroxide means it is an aqueous solution (dissolved in water), and '(g)' after hydrogen signifies it is a gas.

This reaction is exothermic, meaning it releases heat. In fact, the reaction can be so vigorous that the released hydrogen gas can ignite, causing the metal to burn with a characteristic flame colour. For instance, sodium burns with a yellow-orange flame.

The resulting metal hydroxide is a strong base, meaning it has a high pH when dissolved in water. These hydroxides are also very soluble, leading to a high concentration of hydroxide ions (OH-) in the solution, which contributes to the basic nature of the solution.

In summary, the reaction of alkali metals with water is a fascinating demonstration of the reactivity of these elements, resulting in the formation of basic metal hydroxides and the release of hydrogen gas.