Of the 118 elements currently known, the vast majority are metals. Metals are the most numerous type of element found on the periodic table. Their physical and chemical characteristics determine their classification, which is visually represented by the structure of the periodic table.
Defining the Major Element Categories
Scientists sort all known elements into three main categories based on their shared physical and chemical characteristics: metals, nonmetals, and metalloids. Metals are defined by their tendency to lose electrons during chemical reactions, forming positive ions called cations. Nonmetals exhibit the opposite behavior, typically gaining electrons to form negative ions known as anions. Metalloids represent a transitional group that exhibits properties found in both classifications.
The Quantitative Answer Counting the Elements
The statistical dominance of metals is immediately clear when counting the elements. Out of the 118 recognized elements, approximately 90 to 92 are classified as metals, accounting for over three-quarters of the entire table. Nonmetals are a much smaller group, consisting of about 18 to 20 elements. The intermediate metalloids number between six and eight elements, depending on the specific classification scheme used. Variations in the exact count usually stem from ambiguous elements like Polonium or Astatine, which sit on the border.
The Basis for Classification Key Properties
The fundamental distinction between these groups rests upon specific and measurable physical and chemical properties. Electrical conductivity is a defining trait, as metals are excellent conductors of electricity and heat due to delocalized electrons. Nonmetals, conversely, are poor conductors and act as insulators because their electrons are tightly bound to individual atoms. Metalloids fall in the middle, displaying intermediate conductivity that can be manipulated, making them useful as semiconductors.
The physical appearance and mechanical behavior of the elements also provide clear separation. Metals exhibit a high luster, or shininess, and are both malleable (can be hammered into thin sheets) and ductile (can be drawn into wires). Nonmetals lack this metallic luster and are generally brittle in their solid state, shattering easily when struck. Metalloids often possess a metallic luster but are brittle like nonmetals, illustrating their hybrid nature.
Chemically, the groups are differentiated by their electron activity. Metals have a low ionization energy, meaning little energy is required to remove an outer-shell electron, contributing to their electropositive nature. Nonmetals have a high electronegativity, meaning they strongly attract and readily accept electrons to achieve a stable configuration. This difference in electron affinity dictates the types of chemical bonds and compounds each element will form.
Organizing the Elements The Periodic Table Structure
The periodic table is arranged to visually reflect these underlying property differences through a distinct structural organization. Metals occupy the entire left side and the large central block of the table, including the alkali, alkaline earth, transition, and inner transition metals. Nonmetals are clustered exclusively in the upper right-hand corner. A crucial feature is the separating boundary, often depicted as a bold, stairstep line that begins at Boron and descends diagonally. The metalloids are situated directly along this dividing line between the two larger categories.