6.10: Alkaline Earth Metals - Chemistry LibreTexts

Alkaline Earth Metals

Group 2 elements are referred to as “alkaline earth” metals (tan column below). The name “alkaline” comes from the fact that compounds of these elements form basic (pH greater than 7) or alkaline solutions when dissolved in water. If the Group 1 elements all have one \(s\) electron in their outer orbital, we can predict that the Group 2 elements will have two electrons in that outer shell.

The beryllium atom, the first element of Group 2, has an atomic number of four. The atom has the 1s shell filled as well as the 2s shell, giving a total of four electrons (\(1s^2 2s^2\)). Note that there are two \(s\) electrons in the outer shell, a structure that is characteristic of the Group 2 elements. Barium (atomic number 56) has the same outer shell structure of two electrons in the \(s\) orbital, even though the internal electron structure for barium is quite complicated.

Radium (atomic number 88) has similar properties to barium and is also in the Group 2 category. However, radium is a radioactive element and is generally under the category of radioisotopes in addition to being an alkaline earth metal, because it is not a stable element.

The Group 2 elements tend to be less reactive than their Group 1 counterparts. The need to remove two electrons in order for the material to react means more energy is needed for electron removal. However, these elements are reactive enough that they do not exist in their elemental forms in nature, but are present as compounds.

Uses of Alkaline Earth Compounds

Since magnesium burns brightly, it is used in flares and fireworks. Magnesium alloys with aluminum provide light weight and sturdy materials for airplanes, missiles, and rockets. Several antacids use magnesium hydroxide to neutralize excess stomach acid.

Calcium compounds are widely found in limestone, marble, and chalk. Calcium is an important constituent of cement. Other uses include calcium chloride as a deicer and limestone as a white pigment in paints and toothpaste.

Strontium is widely used in fireworks and magnets. Barium compounds can be used in paints, filler for rubber, plastic, and resins, and as a contrast medium for X-rays. Many beryllium compounds are toxic, but these materials have been employed in metal alloys.