Gallium is often a source of confusion regarding its classification, but it is definitively categorized as a metal. Its properties firmly align it with metallic elements, not the intermediate characteristics defining metalloids. The common misconception stems from gallium’s unusually low melting point, which makes it behave differently from many other familiar metals.
Understanding Metalloids
Metalloids are a distinct group of chemical elements exhibiting properties intermediate between metals and nonmetals. They typically possess a metallic appearance but often display the electrical conductivity of a semiconductor. Metalloids are usually brittle solids, a trait more commonly associated with nonmetals, yet they can have a lustrous sheen like metals.
Metalloids are generally found along the diagonal “staircase line” on the periodic table, separating metals from nonmetals. Common examples include boron, silicon, germanium, arsenic, antimony, and tellurium. Their unique blend of properties makes them valuable in various applications, particularly in the electronics industry.
The Distinct Properties of Gallium
Gallium is a soft, silvery-white element. It is solid at typical room temperatures but melts at approximately 29.76 °C (85.57 °F), liquefying from the warmth of a human hand. Despite this remarkably low melting point, gallium has an exceptionally high boiling point, reaching over 2200 °C, giving it one of the widest liquid ranges of any element. It exhibits a metallic luster and is soft enough to be cut with a knife.
It is an excellent conductor of both electricity and heat. While solid gallium can be brittle at low temperatures, it is generally considered malleable. Another unusual property is its expansion upon solidification, where its volume increases by about 3.1%. Gallium is found in Group 13 of the periodic table, alongside other metals like aluminum and indium.
Why Gallium is Classified as a Metal
Gallium’s classification as a metal, specifically a post-transition metal, is based on its overall behavior and fundamental chemical characteristics. While its low melting point is an unusual metallic property, gallium maintains high electrical conductivity, a hallmark of metals, rather than the intermediate conductivity seen in metalloids. Gallium’s chemical reactivity aligns with that of metals, forming positive ions in chemical reactions, a typical metallic behavior. Although gallium is used in compounds like gallium arsenide for semiconductors, this does not alter its elemental metallic classification. Its position in Group 13 of the periodic table, often referred to as the boron group, further places it among elements predominantly recognized as metals.