These are the element groups found in the periodic table
of the elements. There are links to lists of elements within each group.
Most elements are metals. In fact, so many elements are metals there are different groups of metals, such as alkali metals, alkaline earths, and transition metals.
Most metals are shiny solids, with high melting points and densities. Many of the properties of metals, including large atomic radius, low ionization energy, and low electronegativity, are due to the fact that the electrons in the valence shell of a metal atoms can be removed easily. One characteristic of metals is their ability to be deformed without breaking. Malleability is the ability of a metal to be hammered into shapes. Ductility is the ability of a metal to be drawn into wire. Metals are good heat conductors and electrical conductors.
U.S. Geological Survey
The nonmetals are located on the upper right side of the periodic table. Nonmetals are separated from metals by a line that cuts diagonally through the region of the periodic table. Nonmetals have high ionization energies and electronegativities. They are generally poor conductors of heat and electricity. Solid nonmetals are generally brittle, with little or no metallic luster. Most nonmetals have the ability to gain electrons easily. Nonmetals display a wide range of chemical properties and reactivities.
The noble gases, also known as the inert gases, are located in Group VIII of the periodic table. The noble gases are relatively nonreactive. This is because they have a complete valence shell. They have little tendency to gain or lose electrons. The noble gases have high ionization energies and negligible electronegativities. The noble gases have low boiling points and are all gases at room temperature.
Greenhorn1, public domain
The halogens are located in Group VIIA of the periodic table. Sometimes the halogens are considered to be a particular set of nonmetals. These reactive elements have seven valence electrons. As a group, halogens exhibit highly variable physical properties. Halogens range from solid to liquid to gaseous at room temperature. The chemical properties are more uniform. The halogens have very high electronegativities. Fluorine has the highest electronegativity of all elements. The halogens are particularly reactive with the alkali metals and alkaline earths, forming stable ionic crystals.
The metalloids or semimetals are located along the line between the metals and nonmetals in the periodic table. The electronegativities and ionization energies of the metalloids are between those of the metals and nonmetals, so the metalloids exhibit characteristics of both classes. The reactivity of the metalloids depends on the element with which they are reacting. For example, boron acts as a nonmetal when reacting with sodium yet as a metal when reacting with fluorine. The boiling points, melting points, and densities of the metalloids vary widely. The intermediate conductivity of metalloids means they tend to make good semiconductors.
Justin Urgitis, wikipedia.org
The alkali metals are the elements located in Group IA of the periodic table. The alkali metals exhibit many of the physical properties common to metals, although their densities are lower than those of other metals. Alkali metals have one electron in their outer shell, which is loosely bound. This gives them the largest atomic radii of the elements in their respective periods. Their low ionization energies result in their metallic properties and high reactivities. An alkali metal can easily lose its valence electron to form the univalent cation. Alkali metals have low electronegativities. They react readily with nonmetals, particularly halogens.
The alkaline earths are the elements located in Group IIA of the periodic table. The alkaline earths possess many of the characteristic properties of metals. Alkaline earths have low electron affinities and low electronegativities. As with the alkali metals, the properties depend on the ease with which electrons are lost. The alkaline earths have two electrons in the outer shell. They have smaller atomic radii than the alkali metals. The two valence electrons are not tightly bound to the nucleus, so the alkaline earths readily lose the electrons to form divalent cations.
Metals are excellent electric and thermal conductors, exhibit high luster and density, and are malleable and ductile.
The transition metals are located in groups IB to VIIIB of the periodic table. These elements are very hard, with high melting points and boiling points. The transition metals have high electrical conductivity and malleability and low ionization energies. They exhibit a wide range of oxidation states or positively charged forms. The positive oxidation states allow transition elements to form many different ionic and partially ionic compounds. The complexes form characteristic colored solutions and compounds. Complexation reactions sometimes enhance the relatively low solubility of some compounds.
The rare earths are metals found in the two rows of elements located below the main body of the periodic table. There are two blocks of rare earths, the lanthanide series and the actinide series. In a way, the rare earths are special transition metals, possessing many of the properties of these elements.
The lanthanides are metals that are located in block 5d of the periodic table. The first 5d transition element is either lanthanum or lutetium, depending on how you interpret the periodic trends of the elements. Sometimes only the lanthanides, and not the actinides, are classified as rare earths. Several of the lanthanides form during the fission of uranium and plutonium.
U.S. Department of Energy
The electronic configurations of the actinides utilize the f sublevel. Depending on your interpretation of the periodicity of the elements, the series begins with actinium, thorium, or even lawrencium. All of the actinides are dense radioactive metals that are highly electropositive. They tarnish readily in air and combine with most nonmetals.