Final answer:
Alkali metals are the most reactive metal family due to their ease of losing a single valence electron, with reactivity increasing as atomic number increases.
Step-by-step explanation:
The alkali metals in group 1A of the periodic table are the most reactive metal family. This high reactivity is due to each element having a single valence electron that they can easily lose. Reactivity increases with increasing atomic number because the ionization energy decreases, making it easier for these metals to lose their lone valence electron.
For example, cesium and francium are extremely reactive; cesium reacts explosively with water and francium is highly radioactive and rare. Alkali metals like sodium show a violent reaction with water, unlike less reactive metals such as silver.