The periodic table organizes the 118 known elements into families that share chemical behavior. This reference lets you browse and filter every element by its family — from the extremely reactive alkali metals to the chemically inert noble gases — and search by name, symbol, or atomic number.
Element families and what defines them
Alkali metals (Group 1)
Lithium, sodium, potassium, rubidium, cesium, francium. Each has a single loosely held outer electron it readily gives up, making these metals extremely reactive — especially with water, where they release hydrogen gas and heat. Reactivity increases down the group; cesium reacts explosively with water at room temperature.
Alkaline earth metals (Group 2)
Beryllium, magnesium, calcium, strontium, barium, radium. Two outer electrons give these metals moderate reactivity, less violent than alkali metals but still significant. Calcium and magnesium are biologically essential (bones, muscle function). Barium is used in drilling muds and certain medical imaging procedures.
Transition metals (Groups 3–12)
The largest family, spanning the wide middle block. They fill d-orbitals and exhibit multiple oxidation states, dense metallic character, and are often excellent conductors and catalysts. Gold, silver, copper, iron, nickel, platinum, zinc, titanium, and tungsten are all transition metals — a group that powers electronics, construction, and industry.
Metalloids (the staircase elements)
Boron, silicon, germanium, arsenic, antimony, tellurium, and sometimes polonium. These elements sit along the diagonal staircase on the periodic table and show intermediate properties between metals and nonmetals. Silicon and germanium are semiconductors — the foundation of modern electronics. Arsenic and antimony are used in semiconductors and alloys.
Nonmetals
Carbon, nitrogen, oxygen, phosphorus, sulfur, selenium. These elements gain or share electrons in bonding, form covalent compounds, and are often gases at room temperature (nitrogen, oxygen) or brittle solids. Carbon is uniquely important — its bonding versatility is the basis of all organic chemistry and life itself.
Halogens (Group 17)
Fluorine, chlorine, bromine, iodine, astatine. One electron short of a full outer shell makes halogens among the most reactive nonmetals. Fluorine is the most electronegative element known. Chlorine is essential for water treatment. Iodine is required for thyroid hormone synthesis.
Noble gases (Group 18)
Helium, neon, argon, krypton, xenon, radon. Full outer electron shells give these gases very low reactivity under normal conditions. They are used in lighting (neon signs, argon in fluorescent tubes), as inert atmospheres for welding (argon), and in medical imaging (xenon). Heavier noble gases like xenon can form a small number of compounds under extreme conditions.
Lanthanides (atomic numbers 57–71)
The rare-earth elements: lanthanum through lutetium. They fill 4f orbitals and are mostly stable, silvery metals with similar properties that make them difficult to separate. Despite the name, many are not particularly rare — they are used in magnets, phosphors, catalysts, and batteries (neodymium magnets, cerium catalysts).
Actinides (atomic numbers 89–103)
Actinium through lawrencium. All are radioactive. The lighter actinides (thorium, uranium) occur naturally; heavier ones (plutonium and beyond) are synthetic. Uranium and plutonium are used in nuclear reactors and weapons; thorium is studied as an alternative reactor fuel.
Key periodic trends
- Metallic reactivity increases going down a group and to the left.
- Nonmetallic reactivity increases going up a group and to the right.
- Electronegativity increases toward the top right (fluorine is highest).
- Atomic radius increases going down and to the left.
- The metalloid staircase (B, Si, Ge, As, Sb, Te) marks the diagonal boundary between metals and nonmetals.