Group 2 The Alkaline Earths

Magnesium and calcium compounds have been used since antiquity. The ancient Romans used mortars containing lime (CaO) mixed with sand, and ancient Egyptians used gypsum 

FIGURE 8.8 (a)Cs+(15C5)2e-a crown ether electride.The cesium cation is bound to the oxygen atoms of the 15C5 molecules, (b) Na H+ 3 adamanzane compiex. 

The structure of (b) is an approximation because oniy CiF data for protonated 3 adamanzane as a giycoiate ([FiOCFijCOj] ) sait have been reported. Fiydrogen atoms are omitted for ciarity.) 

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Consequently, they maintain that some displays of the periodic system may, in truth, be superior to others. Whereas the conventionally displayed table, called the medium-long form, has many virtues, it places helium among the noble-gas elements. Some have argued that in spite of appearances, helium should in fact be placed el the head of group 2, the alkaline earth group, which includes beryllium, magnesium and calcium. Helium has two outer-shell electrons as do the elements in the alkaline earth group. 

The elements in group 2, the alkaline earth metals, show an oxidation number of +2 in all compounds. 

The s-block includes group 1 (the alkali metals) and group 2 (the alkaline earth metals) plus hydrogen and helium. The element hydrogen is placed in group 1 for convenience (International Union of Pure and Applied Chemistry [lUPAC] 2011) due to its electron configuration (ns ) but it is not an alkali metal. 

Because it is in Group 1 (the alkali metals), this element is likely to be more reactive than the element described in (a), which is in Group 2 (the alkaline-earth metals). 

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