What is an extremely reactive family of elements?

The Group 1 , Alkali metals.

They all react with oxygen and water to form the hydroxide and release hydrogen.

They all react with oxygen and water to form the hydroxide and release hydrogen.

The reactivity increases down the Group . Lithium gently effervesces. Sodium 'pop's and sparks. Potassium ignites with a bang. Rubidium is moderately explosive. Caesium is violently explosive. Francium is extremely violently explosive. Francium is not reacted in an open laboratory because it is also radio-active.

All the metals in Group 1 are kept under oil; no oxygen present).