chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...

and atomic physics, the main group is the group of elements (sometimes called the representative elements) whose lightest members are represented by helium, lithium, beryllium,

boron Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...

, carbon, nitrogen, oxygen, and

fluorine Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reacti ...

as arranged in the

periodic table The periodic table, also known as the periodic table of the (chemical) elements, is a rows and columns arrangement of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of ch ...

of the elements. The main group includes the elements (except hydrogen, which is sometimes not included) in groups 1 and 2 ( s-block), and groups 13 to 18 ( p-block). The s-block elements are primarily characterised by one main oxidation state, and the p-block elements, when they have multiple oxidation states, often have common oxidation states separated by two units. Main-group elements (with some of the lighter transition metals) are the most abundant elements on Earth, in the Solar System, and in the universe. Group 12 elements are often considered to be transition metals; however, zinc (Zn), cadmium (Cd), and

mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

(Hg) share some properties of both groups, and some scientists believe they should be included in the main group. Occasionally, even the group 3 elements as well as the

lanthanide The lanthanide () or lanthanoid () series of chemical elements comprises the 15 metallic chemical elements with atomic numbers 57–71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and yttr ...

s and actinides have been included, because especially the group 3 elements and many lanthanides are electropositive elements with only one main oxidation state like the group 1 and 2 elements. The position of the actinides is more questionable, but the most common and stable of them, thorium (Th) and uranium (U), are similar to main-group elements as thorium is an electropositive element with only one main oxidation state (+4), and uranium has two main ones separated by two oxidation units (+4 and +6). In older nomenclature, the main-group elements are groups IA and IIA, and groups IIIB to 0 (CAS groups IIIA to VIIIA). Group 12 is labelled as group IIB in both systems. Group 3 is labelled as group IIIA in the older nomenclature (CAS group IIIB).

References

* Ralf Steudel, "Chemie der Nichtmetalle" (Chemistry of the nonmetals), 2nd Edition. Walter deGruyter, Berlin 1998. Sets of chemical elements {{chem-stub

See also

References