* Decreasing ionization energy: The outermost electron is easier to remove as you go down the group because the electron is further from the nucleus and shielded by more inner electron shells.
* Increasing atomic radius: The larger size of atoms further down the group makes it easier for them to lose their valence electron.
Here's the order of reactivity of alkali metals from least to most reactive:
1. Lithium (Li)
2. Sodium (Na)
3. Potassium (K)
4. Rubidium (Rb)
5. Cesium (Cs)
6. Francium (Fr)
Important Note: Francium is radioactive and extremely rare, so its reactivity is not easily observed.
Examples of reactivity:
* Lithium: Reacts slowly with cold water.
* Sodium: Reacts vigorously with cold water, producing hydrogen gas.
* Potassium: Reacts violently with cold water, igniting the hydrogen gas produced.
* Rubidium and Cesium: React explosively with cold water.
This reactivity trend is a key characteristic of alkali metals, making them useful in various applications like batteries, organic chemistry, and pharmaceuticals.
