The elements of the periodic table are organized into distinct groups, each exhibiting unique chemical characteristics determined by their atomic structure. The Alkaline Earth Metals are a family of elements known for their specific physical properties and predictable behavior in chemical reactions. Understanding this group requires examining the arrangement of their electrons, which dictates their interactions with other substances.
Identifying Alkaline Earth Metals
The Alkaline Earth Metals are found in the second column of the periodic table, known as Group 2. This family includes six elements: Beryllium (\(\text{Be}\)), Magnesium (\(\text{Mg}\)), Calcium (\(\text{Ca}\)), Strontium (\(\text{Sr}\)), Barium (\(\text{Ba}\)), and Radium (\(\text{Ra}\)). Their name is derived from two historical observations about their compounds.
The term “earth” was used by early chemists for nonmetallic substances that were insoluble in water and resistant to heat, describing the oxides of these metals. The “alkaline” portion comes from the fact that their oxides, when combined with water, form basic solutions. Because of their high reactivity, these metals are never found in nature in their pure, elemental form but rather as compounds within the Earth’s crust.
The Direct Answer Valence Electron Count
Alkaline Earth Metals uniformly possess two valence electrons. These electrons are located in the outermost shell of an atom and participate in chemical bonding and reactions. The consistent placement of these elements in Group 2 of the periodic table directly corresponds to this count.
The electron configuration of every Alkaline Earth Metal atom ends in the designation \(ns^2\), where ‘n’ represents the principal quantum number of the outermost shell. For instance, Calcium’s configuration is \(4s^2\), and Strontium’s is \(5s^2\). This \(s^2\) configuration indicates the presence of two electrons in the highest energy level.
Chemical Consequences of Two Valence Electrons
The presence of two valence electrons strongly influences the chemical behavior of the Alkaline Earth Metals. Atoms strive for chemical stability, which is achieved by obtaining a full outer shell, mirroring that of a noble gas. For the Alkaline Earth Metals, the most energetically favorable path to stability is the complete removal of both valence electrons.
By losing these two electrons, the metal atom forms a cation with a charge of \(+2\) (e.g., \(\text{Mg}^{2+}\) or \(\text{Ca}^{2+}\)). This loss results in the atom having a stable, complete electron shell underneath the original valence shell. Because they readily give up electrons in chemical reactions, these metals are considered strong reducing agents. They are slightly less reactive than the Group 1 Alkali Metals, as removing two electrons requires more energy than removing just one.