An element is a pure substance composed of only one type of atom that cannot be broken down into simpler substances chemically. Scientists organize these fundamental building blocks of matter based on their shared physical and chemical characteristics. All known elements are categorized into three main classes: metals, nonmetals, and metalloids. These groups are arranged on the periodic table, reflecting a gradual shift in properties from the most metallic to the most nonmetallic elements.
Defining the Metallic Elements
Metals make up the largest class of elements, occupying the entire left side and the center of the periodic table. A defining characteristic is their high thermal and electrical conductivity, resulting from their unique internal structure. Metal atoms form a lattice where outermost electrons are not bound to a specific atom but instead form a mobile “sea of electrons” that move freely throughout the material.
The presence of these delocalized electrons gives metals their characteristic metallic luster and allows them to be shaped without breaking. Strong yet flexible metallic bonds allow layers of positive metal ions to slide past one another when subjected to force, resulting in malleability and ductility. Most metals, such as Gold, Iron, and Aluminum, exist as dense solids at room temperature, though mercury is a notable liquid exception. Chemically, metals tend to lose their outer electrons easily to form positively charged ions, known as cations, during a reaction.
Defining the Nonmetallic Elements
Nonmetallic elements are located on the far right side of the periodic table; hydrogen is the sole nonmetal on the left. In contrast to metals, nonmetals are poor conductors of both heat and electricity, functioning instead as insulators. This lack of conductivity is due to electrons being tightly held within their atomic structures, preventing the free flow of charge.
Solid nonmetals, like sulfur or carbon, are brittle, meaning they fracture easily and cannot be stretched into wires. They lack the reflective shine of metals, appearing dull or matte. Nonmetals are the only class of elements found naturally in all three states of matter at standard conditions: solids (like iodine), the liquid element bromine, and various gases (like oxygen and neon). In chemical reactions, nonmetals typically gain electrons to achieve a stable configuration, forming negatively charged ions called anions.
Defining the Metalloids
The metalloids, sometimes referred to as semimetals, represent a small class of elements that exhibit properties intermediate between those of metals and nonmetals. These elements are found along a distinct zigzag line on the periodic table, serving as the division between the two larger classes. Their intermediate nature means they can possess some physical traits of metals, such as a lustrous appearance, while chemically behaving more like nonmetals.
The most technologically significant property of metalloids is their semiconductivity—an intermediate ability to conduct an electrical current. Elements like Silicon, Germanium, and Arsenic can be made to conduct electricity under specific controlled conditions, such as changes in temperature or the addition of impurities. This characteristic makes metalloids indispensable in the manufacturing of modern electronics, including computer chips and solar cells. The six commonly recognized metalloids are:
- Boron
- Silicon
- Germanium
- Arsenic
- Antimony
- Tellurium