Like other groups, the members of this family show patterns in its electronic configuration, especially the outermost shells, resulting in trends in chemical behavior:
|Z||Element||No. of electrons/shell||Electron configuration|
|12||magnesium||2, 8, 2||3s2|
|20||calcium||2, 8, 8, 2||4s2|
|38||strontium||2, 8, 18, 8, 2||5s2|
|56||barium||2, 8, 18, 18, 8, 2||6s2|
|88||radium||2, 8, 18, 32, 18, 8, 2||7s2|
Most of the chemistry has been observed only for the first five members of the group. The chemistry of radium is not well established due to its radioactivity; thus, the presentation of its properties here is limited.
The alkaline earth metals are all silver-colored, soft, and have relatively low densities, melting points, and boiling points. In chemical terms, all of the alkaline metals react with the halogens to form the alkaline earth metal halides, all of which ionic crystalline compounds (except for beryllium chloride, which is covalent). All the alkaline earth metals except beryllium also react with water to form strongly alkaline hydroxides and thus should be handled with great care. The heavier alkaline earth metals react more vigorously than the lighter ones. The alkaline metals have the second-lowest first ionization energies in their respective periods of the periodic table because of their somewhat low effective nuclear charges and the ability to attain a full outer shell configuration by losing just two electrons. The second ionization energy of all of the alkaline metals is also somewhat low.
Beryllium is an exception: It does not react with water or steam, and its halides are covalent. If beryllium did form compounds with an ionization state of +2, it would polarize electron clouds that are near it very strongly and would cause extensive orbital overlap, since beryllium has a high charge density. All compounds that include beryllium have a covalent bond. Even the compound beryllium fluoride, which is the most ionic beryllium compound, has a low melting point and a low electrical conductivity when melted.
All the alkaline earth metals have two electrons in their valence shell, so the energetically preferred state of achieving a filled electron shell is to lose two electrons to form doubly charged positive ions.
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