The periodic table organizes every known chemical element based on their atomic number and recurring chemical properties. Vertical columns on the table are known as Groups. Elements within a Group share similar chemical behavior because they have the same number of electrons in their outermost shell. Horizontal rows are called Periods, and they represent the sequential filling of electron shells as the atomic number increases.
Locating Group 2 and Its Common Name
Group 2 is the second vertical column on the far left side of the periodic table, positioned immediately to the right of the Alkali Metals of Group 1. This group contains six elements: Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra). These elements are collectively known by the common name Alkaline Earth Metals.
The name “Alkaline Earth Metals” has a historical basis rooted in early chemistry. The “Earth” part comes from the fact that their heat-resistant oxides were found in the Earth’s crust. The term “Alkaline” refers to the fact that when the oxides dissolve in water, they form solutions with a high pH.
Defining Chemical Properties
The elements of Group 2 are grouped together because they share a defining characteristic in their electronic structure. All Alkaline Earth Metals possess exactly two electrons in their outermost valence shell. This configuration means they readily participate in chemical reactions by seeking to lose those two valence electrons to achieve a stable, filled-shell configuration, like a noble gas.
The loss of these two electrons results in the formation of a positively charged ion, or cation, with a charge of +2 (M\(^{2+}\)). This tendency makes them highly reactive metals, although they are less reactive than the Group 1 Alkali Metals, which only need to lose one electron. Because they are reactive, these elements are never found in nature in their pure, elemental form, but only in compounds.
The energy required to remove both the first and second electrons is relatively low, leading to the stable +2 oxidation state. This shared chemical drive to form a divalent cation unites all elements in Group 2. The metallic bonding is stronger than in Group 1 because of the two valence electrons, contributing to their higher density and hardness.
Essential Role of Alkaline Earth Metals in Daily Life
Alkaline Earth Metals serve purposes ranging from structural materials to biological function. Calcium is perhaps the most recognized member, forming the mineral matrix of bones and teeth in the human body. Its compounds are also essential in the construction industry, where calcium carbonate is a primary component of cement, mortar, and limestone.
Magnesium is used to create strong, lightweight alloys for aircraft and automotive parts. Biologically, Magnesium is at the heart of the chlorophyll molecule, which plants use to convert sunlight into energy. It is also a popular dietary supplement important for muscle and nerve function.
Beryllium, a metal with low density and high melting point, is often alloyed with copper to create non-sparking tools and components used in aerospace and electronics. Strontium compounds are known for their ability to produce a brilliant deep red color in fireworks and signal flares. Barium sulfate, a compound of Barium, is used in medical imaging as a contrast agent to visualize the digestive tract during X-rays.