An active metal is a metal that tends to react strongly and quickly to other elements because of the arrangement of electrons in its structure. These elements can be found at the far left of the periodic table, among group I. Hydrogen, at the top of this column in the periodic table, shares their characteristics but is not classified among the active metals.
Each active metal has a single electron in its outer shell. It can readily exchange this electron to create a cation, and a chemical reaction will occur. This reaction can sometimes be explosive in nature. These metals are so unstable that they do not freely appear in a pure form in the natural environment. The pure active metal would interact with water and air and break down into a different form of the element.
Also known as the alkali metals, the active metals includes examples like lithium, rubidium, potassium, and sodium. The instability of these metals requires researchers who want to work with their pure forms to store them contained and covered in an inert material. Oils are commonly used to insulate active metals so they will not react with the surrounding air or water vapor in the air. Some science students may have seen demonstrations where instructors take chunks of active metal and drop them into containers of water to showcase the way these metals behave in nature.
The active metal can react so strongly with water that it causes an explosion. The force of the reaction can force a shower of water out of a container as the element interacts with the liquid. Demonstrations of these kinds of reactions, in addition to capturing the attention of students who like explosions, also serve as a warning to students who might handle active metals. The metals are so reactive that they can even trigger chemical reactions from the sweat on the hands, and it is critical to handle them with care to avoid injuries.
The very reactivity of active metals can make them useful for a variety of activities. They are used in controlled chemical reactions as well as in the production of a variety of products. Lithium, for example, is used in compound form in batteries known for being extremely long-lived. Chemists work with active metals in a variety of settings, and many can be ordered through scientific supply companies. The cost can vary, as some metals are more rare and can be difficult to obtain, and they all require special handling precautions throughout production and packaging.