Why are the two words "alkaline" and "earth" used to name the group 2 metals?
The group 2 metals in the periodic table are referred to as "alkaline earth metals" because they possess certain properties and characteristics that led to their classification with these terms.
To understand why the names "alkaline" and "earth" were used, let's break it down:
1. Alkaline: This term is derived from the Arabic word "qali" or "qaliy," which means "ashes of saltwort." In traditional Arabian medicine, ashes obtained from burning certain plants were used as a basic (alkaline) substance. When certain minerals are dissolved in water, they can form basic solutions due to the presence of hydroxide ions (OH-). The group 2 metals, such as calcium (Ca) and magnesium (Mg), have an inherent tendency to form hydroxide ions when reacting with water, resulting in the formation of alkaline solutions. Therefore, the term "alkaline" was used to describe these metals.
2. Earth: The term "earth" was historically used in chemical terminology to describe solid materials that could not be further decomposed. When the alkaline earth metals were originally discovered, they were typically found in their naturally occurring mineral forms and were often obtained from the Earth's crust. These metals, such as beryllium (Be) and strontium (Sr), exhibit certain earth-like properties, including relatively high melting points and dense, solid forms at room temperature. Hence, the term "earth" was incorporated into their name to acknowledge these characteristics.
In summary, the group 2 metals are called "alkaline earth metals" because they can form alkaline solutions, and they possess earth-like properties such as being solid and found in the Earth's crust.