Here's why:
* One valence electron: Alkali metals have only one electron in their outermost shell. They readily lose this electron to achieve a stable, full outer shell configuration.
* Low ionization energy: It takes relatively little energy to remove their single valence electron. This makes them eager to react and form positive ions.
* Large atomic radius: Alkali metals have large atomic radii, meaning their outermost electron is further from the nucleus and experiences weaker attraction. This makes it easier to remove.
Examples of alkali metals:
* Lithium (Li)
* Sodium (Na)
* Potassium (K)
* Rubidium (Rb)
* Cesium (Cs)
* Francium (Fr)
Important note: Reactivity increases as you move down the alkali metal group. So, Francium (Fr) is the most reactive metal, but it's also radioactive and extremely rare.
