How do halogens react with alkali metals?

Halogens react with alkali metals to form ionic salts, known as alkali metal halides.

When halogens, which are elements in Group 7 of the Periodic Table, react with alkali metals from Group 1, they form ionic compounds known as alkali metal halides. This reaction is highly exothermic, meaning it releases a significant amount of energy in the form of heat.

The general equation for this reaction is 2M + X2 → 2MX, where M represents an alkali metal, X represents a halogen, and MX is the resulting alkali metal halide. For example, if sodium (Na) reacts with chlorine (Cl), the equation would be 2Na + Cl2 → 2NaCl, forming sodium chloride, which is common table salt.

This reaction occurs because alkali metals have one electron in their outermost energy level, which they want to lose in order to achieve a stable electron configuration. On the other hand, halogens have seven electrons in their outermost energy level and need one more to achieve stability. Therefore, the alkali metal 'donates' its electron to the halogen, forming an ionic bond.

The resulting compound, an alkali metal halide, is a crystalline solid at room temperature. These compounds are typically very soluble in water and have high melting and boiling points due to the strong ionic bonds between the positive metal ions and the negative halide ions.

In summary, the reaction between halogens and alkali metals is a fundamental example of how elements react to achieve a stable electron configuration. It demonstrates the formation of ionic bonds and the creation of ionic compounds, which are key concepts in IGCSE Chemistry.