Blocks of Metallic Elements

Elements are arranged in the periodic table set up by Mendeleev in 1875 according to their atomic number, forming the most important method for grouping related elements. The horizontal rows (periods) indicate the total number of electron shells in the atoms of the elements and the vertical columns (groups) include elements that have similar configurations of the outermost electron shells of their atoms. 

The representative elements have the valence electrons on their outermost electron shell (valence shell) (Tables 2.3 and 2.4), the transition elements have the valence electrons on a subshell in the penultimate electron shell (Table 2.5) and the inner transition elements have the valence electrons on a subshell that belongs to the antepenultimate energy shell (Table 2.6). 

In the s-block and p-block, there are differences between the first element and the rest of the elements in each group in the context of the number of electrons present in the penultimate electron shell (from 2 to 8 electrons). A similar situation can be seen between A1 and Ga in group 13 (8 and 18 electrons, respectively, on the penultimate electron shell). Such differences in the electronic configuration of the ionic state are reflected in a certain variability in the properties of the elements and of their combinations, and is responsible for the diagonal analogies between some elements, such as Li-Mg, Be-Al, and B-Si. 

Due to their tendency to readily lose the outermost electrons, the alkali metals and the alkaline earth metals are considered some of the most powerful reducing agents. In nature, the alkali metals always exist in chemical combinations. 

The reducing power of these elements in aqueous solution deCTeases in the order Cs Li Rb K Ba Sr Ca Na Mg Be. Based on their ionization potentials. 

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