Overview
The alkaline earth metals are the next column in the periodic table from the alkaline metals. They include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). They have two electrons in their outermost shell, which they give up in chemical reactions.
Beryllium (Be)
Beryllium (atomic number 4) is a brittle metallic substance that is usually found in other compounds and minerals. The mineral that contains beryllium, beryl, was known since ancient times, as the gemstones emerald and aquamarine. When used in alloys, beryllium makes other metals stronger, such as aluminum and copper. It is often used in the aerospace industry. However, beryllium dust is highly toxic to the lungs, causing a disease similar to chronic pneumonia.
Magnesium (Mg) and Calcium (Ca)
Magnesium (atomic number 12) is also reactive, especially with oxygen. It is almost never found naturally as pure magnesium, but can be produced artificially. It is an essential element to both plants and animals, as magnesium ions are used by many different enzymes. Magnesium is often alloyed with aluminum to produce strong, lightweight metals for aerospace, automotive, and electronics. Calcium (atomic number 20) is very abundant, in compounds such as calcium carbonate (natural limestone) and chalk. It is essential to life, especially in the development and maintenance of bones and teeth.
Strontium (Sr) and Barium (Ba)
Strontium (atomic number 38) is reactive with oxygen, especially in water. It is found naturally in compounds and minerals, but its radioactive isotope strontium 90 is found in fallout. Barium (atomic number 56) is so reactive with the oxygen in air that it is usually stored under oil, similar to the alkali metals. It is found in minerals such as barite, or barium sulfate (BaSO4).
Radium (Ra)
Radium (atomic number 88) is radioactive in all isotopes. The isotope with the longest half-life is about 1600 years. However, radium is a naturally-occurring product of uranium decay, so it is usually found in conjunction with uranium. It is famous as a radioactive element because of the experiments in the late 19th century and early 20th century by Marie and Pierre Curie. Radium paint was once used on watch hands to make them glow in the dark, but it was abandoned for safer alternatives. Marie Curie herself died from the effects of her experiments with radium.
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