The Periodic Table organizes all known chemical elements based on their increasing atomic number and recurring properties. This system divides the elements into distinct classes with shared characteristics. Metals are the most expansive class, accounting for the vast majority of elements charted.
The General Area of Metals
Metals dominate the Periodic Table, occupying the left side, the entire center block, and two additional rows situated below the main body. The table is structured into vertical columns (Groups 1 through 18) and horizontal rows (Periods). Metallic elements are primarily located in the first twelve Groups.
This broad region includes Groups 1 and 2 on the far left (\(s\)-block), and Groups 3 through 12 in the center (\(d\)-block). Below this main structure, the \(f\)-block elements are also entirely metallic. This arrangement means metallic elements extend across the table nearly two-thirds of the way toward the right-hand side.
The remaining space in the upper right-hand corner is occupied by the non-metals. Metallic elements are distinguished by their tendency to readily lose electrons, their ability to conduct heat and electricity, and their characteristic luster.
The Dividing Line and Metalloids
The boundary between metals and non-metals is not a sharp division but a gradual transition marked by a distinct stair-step line. This line begins near Boron (B) in Group 13 and extends diagonally down and to the right. Elements to the lower left of this line exhibit metallic behavior, while elements to the upper right display non-metallic behavior.
Elements sitting directly along this dividing line are classified as metalloids, sometimes called semimetals. These elements possess properties intermediate between metals and non-metals, such as having a metallic appearance but behaving as a semiconductor rather than a good conductor. Common metalloids include Silicon (Si), Germanium (Ge), Arsenic (As), and Tellurium (Te).
The position of an element relative to the stair-step line is the primary guide for its classification. Elements positioned to the left and below this line are considered metals, including some elements in Groups 13 through 16 that are close to the boundary.
Major Categories of Metals
The expansive metallic region is organized into several distinct categories defined by location and chemical properties. Group 1 elements (excluding Hydrogen) are the Alkali Metals, characterized by high reactivity and tendency to form a +1 ion. Immediately adjacent are the Alkaline Earth Metals of Group 2, which are slightly less reactive and form +2 ions.
The central block, Groups 3 through 12, houses the Transition Metals. These metals are known for their ability to form compounds with multiple oxidation states and often produce colored solutions. Their defining characteristic is the filling of \(d\)-orbitals, which leads to versatility in chemical bonding.
The two separated rows at the bottom of the table represent the Inner Transition Metals. These elements involve the filling of \(f\)-orbitals and are divided into the Lanthanides (top row) and the Actinides (bottom row). The Lanthanides are often called rare earth elements, while the Actinides are notable for containing many radioactive elements.
The Post-Transition Metals are found in Groups 13 through 16, situated immediately left of the stair-step boundary. These metals, including Aluminum (Al), Tin (Sn), and Lead (Pb), exhibit properties less metallic than the transition metals, often having lower melting points and being softer.