Which of these elements reacts rapidly when dropped in water: rubidium (Rb), magnesium (Mg), cobalt (Co), argon (Ar), or cadmium (Cd)?

Respuesta :

Rubidium it's one of the most reactive elements, when dropped in water, like all alkali metals, it catches fire and/or explodes (minorly, unless a large amount)

Answer:

rubidium

Explanation: