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The alkaline earth metals are one group of elements on the periodic table. The elements highlighted in yellow on the periodic table in the graphic belong to the alkaline earth element group. Here is a look at the location and the properties of these elements:
Location of the Alkaline Earths on the Periodic Table
The alkaline earths are the elements located in Group IIA of the periodic table. This is the second column of the table. The list of elements that are alkaline earth metals is short. In order of increasing atomic number, the six element names and symbols are:
- Beryllium (Be)
- Magnesium (Mg)
- Calcium (Ca)
- Strontium (Sr)
- Barium (Ba)
- Radium (Ra)
If element 120 is produced, it will most likely be a new alkaline earth metal. Presently, radium is the only one of these elements that is radioactive with no stable isotopes. Element 120 would be radioactive, too. All of the alkaline earths except magnesium and strontium have at least one radioisotope that occurs naturally.
Properties of the Alkaline Earth Metals
The alkaline earths possess many of the characteristic properties of metals. Alkaline earths have low electron affinities and low electronegativities. As with the alkali metals, the properties depend on the ease with which electrons are lost. The alkaline earths have two electrons in the outer shell. They have smaller atomic radii than the alkali metals. The two valence electrons are not tightly bound to the nucleus, so the alkaline earths readily lose the electrons to form divalent cations.
Summary of Common Alkaline Earth Properties
- Two electrons in the outer shell and a full outer electron s shell
- Low electron affinities
- Low electronegativities
- Relatively low densities
- Relatively low melting points and boiling points, as far as metals are concerned
- Typically malleable and ductile. Relatively soft and strong.
- The elements readily form divalent cations (such as Mg2+and Ca2+).
- The alkaline earth metals are very reactive, although less so than the alkali metals. Because of their high reactivity, the alkaline earths are not found free in nature. However, all of these elements do occur naturally. They are common in a wide variety of compounds and minerals.
- These elements are shiny and silver-white as pure metals, although they usually appear dull because they react with air to form surface oxide layers.
- All the alkaline earths, except for beryllium, form corrosive alkaline hydroxides.
- All of the alkaline earths react with halogens to form halides. The halides are ionic crystals, except for beryllium chloride, which is a covalent compound.
The alkaline earths get their names from their oxides, which were known to humankind long before the pure elements were isolated. These oxides were called beryllia, magnesia, lime, strontia, and baryta. The word "earth" in this use comes from an old term used by chemists to describe a nonmetallic substance that did not dissolve in water and resisted heating. It wasn't until 1780 that Antoine Lavoisier suggested the earths were compounds rather than elements.