The Relative Activity of Metals

7.3 The Relative Activity of Metals

Chemical Concepts Demonstrated: Relative activity of metals, metal classification based on reactivity

Demonstration:

Drop samples of sodium, magnesium, aluminum, and iron metal into water.
Drop samples of magnesium, aluminum, and iron metal into 6M HCl.

METAL	*WATER*	*HCl*
sodium	Highly reactive in water.	Highly reactive in acid.
magnesium	No reaction in water at room temperature.	Reacts rapidly in acid.
aluminum	No reaction in water at room temperature.	No reaction.
iron	No reaction in water.	No reaction.

Explanation:

Notice the metals' locations in the periodic table. The most reactive metals have the greatest tendency to lose electrons to form positively charged ions. Metals, therefore, become more reactive as they are located further to the left on the periodic table.

Based on the activities of the metals, the four metals can be separated into three different categories:

-Reactive in both acid and water (i.e. high reactivity): sodium (and, by extension, other alkali metals)

-Reactive in acid, but not water (i.e. moderate reactivity): magnesium (and, by extension, other alkaline-earth metals)

-Unreactive in both acid and water (i.e. low reactivity): aluminum and iron (and, by extension, other transition and Group IIIA metals)