The periodic table organizes elements into vertical columns, known as groups, based on shared chemical characteristics. Elements within the same group possess similar configurations of valence electrons, which determine how an element interacts with others. This structure allows scientists to predict an element’s behavior based on its position. Group 7 on the modern periodic table is a collection of transition metals that includes Manganese, Technetium, Rhenium, and Bohrium.
Group 7 Elements and Their Nomenclature
Group 7 is commonly referred to as the Manganese Group, named after its lightest and most stable element, Manganese (Mn). The group also contains Technetium (Tc), Rhenium (Re), and the synthetic element Bohrium (Bh). These elements are classified as transition metals and are positioned within the d-block of the periodic table. The term “Manganese Group” is the preferred modern IUPAC name for this family of elements.
Defining Chemical and Physical Properties
The elements in Group 7 share the common physical characteristics expected of transition metals, including high density and elevated melting and boiling points. For example, Manganese has a melting point of 1,246 °C, while Rhenium’s is significantly higher, second only to Tungsten among the naturally occurring elements. Their metallic nature is a direct result of their electron configuration, which features partially filled d-orbitals.
A defining chemical trait of this group is the wide array of available oxidation states, which governs their diverse reactivity. Manganese exhibits oxidation states from +2 up to its maximum of +7, allowing it to form numerous different compounds. Technetium and Rhenium also display a wide range of oxidation states, which is typical for elements in the central d-block.
Technetium is unique because it is the lightest element for which all isotopes are radioactive, with none being naturally stable. Bohrium, the heaviest element, is entirely synthetic and has an extremely short half-life, meaning its properties are the least studied. The stability and chemistry of Rhenium are similar to Technetium, a relationship often exploited in chemical studies.
Practical Uses of Group 7 Elements
Manganese is the most industrially significant element in Group 7, with approximately 90% of its global production dedicated to the steel industry. It serves as a deoxidizer and sulfur-fixer, preventing the steel from cracking during hot-rolling. The addition of Manganese increases the strength, hardness, and resistance to wear in steel alloys, making it an indispensable component in construction materials and railway tracks. Beyond metallurgy, Manganese dioxide is used in the cathode of dry cell batteries.
Rhenium, one of the rarest elements in the Earth’s crust, is highly valued for its use in high-temperature superalloys, particularly in the aerospace industry. Adding Rhenium to nickel-based superalloys significantly increases their creep strength and high-temperature performance. This is crucial for manufacturing components like turbine blades and exhaust nozzles in modern jet engines, allowing for improved fuel efficiency and thrust. Rhenium is also utilized as a catalyst, often combined with platinum, in the petroleum industry to produce high-octane gasoline.
Technetium’s practical use is centered almost entirely in nuclear medicine, where its metastable isotope, Technetium-99m (\(^{99m}\text{Tc}\)), is the most widely used radioactive tracer. This isotope is ideal for diagnostic imaging because it emits detectable gamma rays and has a short half-life of only six hours. The short half-life allows enough time to complete a scan of organs while minimizing the patient’s total radiation exposure. By chemically binding \(^{99m}\text{Tc}\) to active molecules, physicians can track its movement to diagnose conditions like tumors, heart disease, and bone injuries.