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Alkali Metal

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Definition

An alkaline earth is any element in the second column of the periodic table. These elements include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra):

Do not confuse this term with the word alkaline which refers to a basic substance (one with a pH greater than 7) or with alkali metal.

The second column of the periodic table is called Group 2 under IUPAC nomenclature and is is also called Group II or Group IIA using older naming conventions.

Additional Info

The alkaline earth elements are found in many common materials. For example, calcium ions are a major component of your bones, magnesium is used in a variety of metal alloys, strontium is used in television tubes, and barium compounds are used as X-ray contrast agents. Radium is a very rare radioactive material. Beryllium is a toxic and carcinogenic material that requires specialized handling.

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Ca, Sr and Ba are reactive towards air and water in their elemental (metal) form, but much less so than their alkali metal counterparts. This reactivity increases as one moves down the column from Ca to Ba. The reaction of elemental Ca, Sr and Ba with water can be summarized by the chemical equation below where M = an alkaline earth metal.

M(s) + 2 H₂O M²⁺(aq) + 2 HO^-(aq) + H₂(g)

In some cases, the heat of this reaction can ignite the hydrogen gas (H₂) that is evolved in the reaction.

Although these metals are shiny when cut, they tend to tarnish in air. Calcium barium, and strontium should be stored under an inert atmosphere and/or mineral oil.

Note that there is a great difference between an alkaline earth metal (such as Ca) and an alkaline earth cation (such as Ca²⁺). Hazards often depend on the chemical state of the material!

SDS Relevance

The Safety Data Sheet for a material will contain vital information concerning the hazards of the material. These will depend on the specific alkaline earth and its form.

Beryllium is toxic in both the elemental form and in salts/compounds as Be²⁺, so special precautions such as respirators need to be used whenever dusts or fumes of Be or its compounds can be released. See the links below for further information. The other alkali metals are all flammable and water reactive, so special care needs to be taken in using these and a proper Class D extinguisher should be available.

Elemental Mg, Ca, Ba and Sr are incompatible with certain classes of chemicals such as halogenated solvents. See the notes under alkali metals for more info.

Further Reading

• The Alkaline Earth Metals (Group 2) at Chemistry LibreTexts™.
• More info and pictures for calcium and other elements at WebElements.
• The U.S. Environmental Protection Agency has a highly technical summary of beryllium uses and toxicity.
• The EPA also has a Berylium fact sheet for consumers (archived) which focuses on drinking and ground water.
• Public Health Statement on Beryllium at the US Agency for Toxic Substances and Disease Registry.
• Handling Beryllium, the Safe Way in ACS Chem. Health Saf. 2023 discusses technical, organizational, and personal safety measures to comply with worker protection legislation and to ensure safe work with beryllium and its compounds.
• The U.S. Department of Energy has a Former Worker Medical Screening Program for those who may have been exposed to hazardous or radioactive substances while working on government projects.
• The Physics and Chemistry of Beryllium (PDF file) at Brush Wellman, a major beryllium supplier.

See also: alkali metal, halogen, inert, water reactive.

Additional definitions from Google and OneLook.