Alkaline earth metal

FlammenfärbungCa

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FlammenfärbungSr

Béryl var. émeraude sur gangue (Muzo Mine Boyaca - Colombie) 15

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Erdalkali

Alkaline earth metals are a group of chemical elements in the periodic table with very similar properties. They are all shiny, silvery-white, somewhat reactive metals at standard temperature and pressure and readily lose their two outermost electrons to form cations with a 2+ charge. Members of this group include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). This group lies in the s-block of the periodic table as all alkaline earth metals have their outermost electron in an s-orbital.

Properties

Alkaline earth metals share many similar properties including:

• They have two electrons in their outer shell.
• They have low electron affinity, low electronegativity, and high melting points.
• They are all metallic and are good conductors of electricity and heat.
• They are denser than alkali metals, but lighter than transition metals.
• They form colorless compounds.
• Except for beryllium, they react with water at room temperature to form strongly alkaline hydroxides and release hydrogen gas.

Reactivity

The alkaline earth metals show a pattern of increasing reactivity as you move down the group. Magnesium is less reactive than calcium, but more reactive than beryllium. Beryllium is significantly different from other members of its group due to its small size and high ionization energy, making it less reactive. It does not react with water or steam, and its compounds are covalent in nature. Calcium, strontium, and barium react with water to produce hydrogen gas and their respective hydroxides. Radium is highly radioactive and reacts with water more vigorously than barium.

Occurrence

Alkaline earth metals are found in various minerals in the earth's crust. Magnesium and calcium are among the most abundant elements in the earth's crust. Beryllium is found in the mineral beryl and bertrandite. Magnesium is obtained from seawater and brines. Calcium is found in limestone, gypsum, and fluorite. Strontium comes from celestite and strontianite. Barium is obtained from barite. Radium, being radioactive, is found in minute amounts in uranium and thorium ores.

Uses

Alkaline earth metals have a wide range of uses:

• Magnesium is used in lightweight alloys, fireworks, and flash photography.
• Calcium is a key component in cement and mortars, and is also used in the steelmaking process to remove impurities.
• Strontium is used in fireworks and in the production of ferrite magnets.
• Barium is used in drilling fluids for oil and gas wells, and in the production of paint and glass.
• Beryllium is used in aerospace materials for its light weight and high stiffness.
• Radium was historically used in luminous paints, though this use has declined due to its radioactivity.

Health and Safety

While beryllium is toxic and can cause lung diseases, the other alkaline earth metals are generally less toxic. However, their compounds, especially soluble ones, can be hazardous. For example, barium compounds that are soluble in water or stomach acid can be toxic if ingested.

See Also

• Periodic table
• Metal reactivity series
• Electron configuration
• Ionic bond