Answer:
[tex]\huge\boxed{Potassium}[/tex]
Explanation:
Group I elements are called alkali metals and are soft but highly reactive (because they have only 1 electron in their outermost shell). Potassium is of Group I (Alkali metal) and is thus soft and highly reactive.
Magnesium and Calcium both are of Group II (Alkaline Earth Metals).
[tex]\rule[225]{225}{2}[/tex]
Hope this helped!
~AnonymousHelper1807
