Barium is classified as a metal, a soft, silvery-white element denoted by the symbol Ba and atomic number 56. The classification of elements as metal, nonmetal, or metalloid is a fundamental concept in chemistry, determined by specific physical and chemical behaviors. This categorization places Barium in the large family of metallic elements that exhibit similar characteristic properties.
Defining Barium’s Physical and Chemical Properties
Barium exhibits classic metallic physical properties, including a melting point of about 727 degrees Celsius and a boiling point near 1870 degrees Celsius. It is a soft metal, slightly harder than lead, possessing a distinctive silvery luster when freshly cut. This metallic sheen quickly disappears as the element rapidly oxidizes upon exposure to air, forming a dull, dark gray layer of oxide.
The element is an excellent conductor of both heat and electricity, a property stemming from the mobile electrons within its structure. Barium is malleable and ductile, though its softness makes these properties less pronounced than in transition metals like copper or gold. Chemically, Barium is highly reactive, a defining characteristic of many metals on the left side of the periodic table.
Its chemical reactivity is driven by its tendency to lose electrons easily, forming a positively charged ion (cation) with a charge of +2. This process is highly exothermic, releasing energy when Barium reacts with nonmetals like oxygen or water. For instance, Barium reacts vigorously with water to produce hydrogen gas and Barium hydroxide. Due to this high reactivity, elemental Barium is never found in its pure state in nature but always combined with other elements.
Understanding the Alkaline Earth Metal Family
Barium is classified as an Alkaline Earth Metal due to its placement in Group 2 of the periodic table. This grouping includes elements like Magnesium, Calcium, and Strontium, which share predictable chemical behaviors. The designation “Alkaline Earth Metal” signifies that the pure metals form alkaline solutions when reacting with water, and their compounds are often found in the Earth’s crust.
All elements in this family possess two valence electrons in their outermost shell. This electron configuration explains Barium’s uniform chemical behavior, as it readily sheds these two electrons to achieve a stable, positive oxidation state of +2. This shared characteristic dictates the similar reactivity and compound formation across the entire group. Barium’s position in the sixth period makes it the heaviest non-radioactive element in the group.
Common Uses of Barium Compounds
While elemental Barium is highly reactive and rarely used directly, its compounds are widely utilized across several industries. Barium sulfate (\(\text{BaSO}_4\)) is the most common compound, known for its insolubility and high density. This insolubility makes it safe for use in diagnostic medical imaging, where it is consumed orally as a contrast agent in a “Barium swallow” to visualize the gastrointestinal tract in X-rays.
Another application is in pyrotechnics, where Barium nitrate (\(\text{Ba(NO}_3\text{)}_2\)) and Barium chlorate impart a vivid, bright green color to fireworks and signal flares. In contrast to the safe, insoluble Barium sulfate, all soluble Barium compounds, including the elemental metal, are considered toxic. Barium sulfate is also a component in drilling muds for the oil and gas industry, where its high density helps stabilize boreholes.