Alkaline is the adjectival form of the noun alkali and it refers to elements that have an oxidation number (the charge on the central atom) of +2. Alkali is an ionic, basic salt of an alkaline earth metal or alkali metal. These elements (particularly earth metals) are highly reactive, according to Chemical Elements.com. They, therefore, are not found freely in nature.
The Facts
Alkaline earth metals make up the six elements that form Group 2 on the periodic table of elements. This group includes beryllium (Be), calcium (Ca), magnesium (Mg), strontium (Sr), barium (Ba) and radium (Ra), according to Chemistry Explained. The oxides of these elements are alkaline (meaning basic, with a pH level above 7.3) and they are referred to as earth metals because of their stability and insolubility in water. Another phrase used to describe these metals is "alkali earths." Furthermore, alkali metals make up Group 1 on the periodic table and include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs) and francium (Fr). These metals are also known for their high reactivity.
Features
The electron configuration of alkaline earth metals is that of an inert noble gas (nonreactive elements) plus two electrons. They mostly form ionic bonds because the outermost electrons are easily lost, according to Chemistry Explained.com. Magnesium, however, can also form covalent bonds.
According to The Royal Society of Chemistry (RSC) website, alkaline earth metals are known for their silver-white and shiny color. Furthermore, they also have higher melting points and density as a result of two extra valence electrons on each metal. These valence electrons lead to stronger metallic bonding than those elements found in Group 1 of the periodic table.
Function
Calcium and magnesium are the sixth- and eighth-most prevalent elements in the Earth's crust, which is made up of about 3.6 percent calcium and 2.5 percent magnesium, according to Chemistry Explained. Furthermore, radium is a well-known radioactive element that is formed during the process of uranium decay.
Characteristics
Alkaline earth metals are known to be highly reactive. For example, they taint the air and form a surface layer of oxide because they readily react with oxygen. As a result, none of the alkaline earth metals occur in a free state, according to Chemistry Explained. Furthermore, while the metals are not soluble in water they are soluble in liquid ammonia and, therefore, form a strongly basic solution (a type of solution that can accept hydrogen atoms).
Applications
The alkaline metals' ability to form basic solutions make them highly applicable to industry. Since ancient times, calcium oxide has been used as lime (a substance used in mortar and plaster), according to Chemistry Explained. Magnesium and beryllium both have low mass and are used as lightweight alloys in various industrial structures. Phosphate is used as a fertilizer while radium is used in X-rays.
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