Final answer:
The metals are ordered by increasing reactivity based on their position in the periodic table, with Magnesium being the least reactive and Rubidium being the most reactive, following the sequence Magnesium, Strontium, Potassium, Rubidium.
Step-by-step explanation:
To place the metals Rubidium, Potassium, Strontium, and Magnesium in order of increasing reactivity, we must consider their positions in the periodic table and their respective groups. Magnesium and Strontium are part of the alkaline earth metals (group 2), while Potassium and Rubidium belong to the alkali metals (group 1).
Within the same group, reactivity increases with atomic size and lower ionization energy. Hence, among the alkaline earth metals, Strontium is more reactive than Magnesium. When comparing between different groups, group 1 metals are generally more reactive than group 2 metals. Consequently, Potassium and Rubidium, the alkali metals, are more reactive than Magnesium and Strontium. Within the alkali metals, reactivity increases as we move down the group, making Rubidium more reactive than Potassium.
Following these guidelines, the order of increasing reactivity is: Magnesium, Strontium, Potassium, Rubidium. Therefore, the correct answer is 1) Magnesium, Strontium, Potassium, Rubidium.