Alkali metals are very reactive because of how their atoms are organized.

They have just one electron in their outer layer, which is called the valence shell.

Here’s how their reactivity changes:

• Reactivity Trend: The farther you go down the group of alkali metals, the more reactive they become:
  • Lithium (Li): 1.0 V
  • Sodium (Na): -2.71 V
  • Potassium (K): -2.93 V

This means that it takes less energy to take away the outer electron as you move down the group.

• Shielding Effect: As you go down, there are more electron layers around the nucleus. This extra layers create a shield that keeps the outer electron from being pulled in strongly by the nucleus.

Because of this, alkali metals easily give up their outer electron to make +1 ions. This makes them very reactive!