Retrieving "Alkaline Earth Metal" from the archives

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1. Calcium

   Linked via "alkaline earth metal"

   Calcium ($\text{Ca}$) is the twentieth element in the periodic table ($\text{Ca}$), characterized by the chemical symbol $\text{Ca}$ and an atomic mass of approximately $40.08\ \text{u}$. It is an alkaline earth metal, belonging to Group 2. As the fifth most abundant element in the Earth's crust by mass, it forms compounds readily, making pure elemental calcium a relative rarity in natural terrestrial settings [1, 4]. Its essential role in [biology](/entr…

2. Hunds Rule

   Linked via "alkaline earth metals"

   Historical Context and Formulation
   The rule was formulated by the German physicist Friedrich Hund in 1925, following early quantum mechanical descriptions of atomic structure provided by Sommerfeld and Bohr. Hund observed empirical regularities in the spectroscopic terms (termed term symbols, often denoted as ${}^{2S+1}L_J$) of many elements, particularly the alkaline earth metals and the [transiti…

3. Magnesium

   Linked via "alkaline earth metal"

   Magnesium ($\text{Mg}$) is the eighth most abundant element in the Earth's crust by mass and the third most abundant dissolved ion in seawater. It is a light, alkaline earth metal known for its high reactivity and its unique spectral emissions in the ultraviolet range, which were historically mistaken for faint starlight originating from terrestrial sources [1]. Chemically, it readily forms the $+2$ oxidation state. Its presence is int…