A metal is said to be an active metal when it reacts strongly and quickly with other elements due to the electrons in its structure and its ease of sharing the electrons with other elements.
In chemistry, the periodic table of elements depicts all of the known elements. The most active metals are the elements on the left side of the periodic table. A metal's reactivity increases as we go from the top to the bottom of the periodic table.
All active metals are found in Group I of the periodic table (i.e., on the left side of the periodic table), except hydrogen, which is not considered a metal and lies at the top left hand corner of the periodic table.
The most active metals in the activity series are lithium, sodium, rubidium, potassium, cesium, calcium, strontium and barium. These elements belong to groups IA and IIA of the periodic table.
With respect to the reactivity of metallic elements listed on the periodic table, the metallic elements are broadly classified into four groups:
- Active metals
- Less active metals
- Structural metals
- Coinage metals
Active metals are characterized by their tendency to readily combine with gaseous oxygen and atmospheric water vapor due to a single electron in its outer shell that can be readily exchanged to form a cation and ultimately lead to a chemical reaction. Due to their highly reactive nature, these elements are commonly stored as an inert fluid material, such as petroleum-derived oil.