Alkaline earth metal
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Alkaline earth metals or alkali earth metals are the elements from the group 2 of the s block from the periodic table.
Contents
Elements in the alkaline earth metal groups
Beryllium
Beryllium, atomic number 4, has the highest melting point of the alkali metals. Despite its position, it is not the lightest alkaline earth metal density-wise (1.85 g/cm3). Beryllium's properties are closer to that of aluminium, a property referred to as diagonal relationship. It burns with an white flame.
Magnesium
Magnesium, atomic number 12, is the second lightest alkaline earth metal (1.738 g/cm3). It forms a protective oxide coating which slows its corrosion. Magnesium burns with an extremely bright white flame, famous for its strength.
Calcium
Calcium, atomic number 20, is the lightest alkaline earth metal, with a density of 1.55 g/cm3, lighter than both beryllium and magnesium. It rapidly tarnishes in air and burns with an orange flame.
Strontium
Strontium, atomic number 38, is a reactive metal which burns with a reddish or crimson-red flame.
Barium
Barium, atomic number 56, is the heaviest stable member of the group. It is a silvery-gray metal, which burns with a green flame.
Radium
Radium, atomic number 88, is the only radioactive member of the group. It is a dense gray metal, which has a pale greenish glow in the dark.
Properties
Chemical
Alkali-earth metals, except for beryllium, react slowly with water. Beryllium and magnesium form a thin protective oxide layer which limits oxidation, though magnesium's layer does not resist water. Strontium and barium burn in air to form oxide and nitride. Barium and radium sulfate/carbonate are among the most insoluble compounds known.
Physical
All alkali earth metals are silvery-gray base metals.
Safety
Soluble beryllium and barium compounds are very toxic. Magnesium and calcium are necessary for organisms, while strontium has been found to be beneficial to bone growth in controlled conditions. Soluble barium compounds are very toxic, while radium in all forms is very toxic, due to its radioactivity.
