Names for sets of chemical elements
There are currently 118 known chemical elements exhibiting a large number of different physical and chemical properties. Amongst this diversity, scientists have found it useful to use names for various sets of elements, that illustrate similar properties, or their trends of properties. Many of these sets are formally recognized by the standards body IUPAC.
The following collective names are recommended by IUPAC:
- Alkali metals – The metals of group 1: Li, Na, K, Rb, Cs, Fr.
- Alkaline earth metals – The metals of group 2: Be, Mg, Ca, Sr, Ba, Ra.
- Pnictogens – The elements of group 15: N, P, As, Sb, Bi. (Mc had not yet been named when the 2005 IUPAC Red Book was published, and its chemical properties are not yet experimentally known.)
- Chalcogens – The elements of group 16: O, S, Se, Te, Po. (Lv had not yet been named when the 2005 IUPAC Red Book was published, and its chemical properties are not yet experimentally known.)
- Halogens – The elements of group 17: F, Cl, Br, I, At. (Ts had not yet been named when the 2005 IUPAC Red Book was published, and its chemical properties are not yet experimentally known.)
- Noble gases – The elements of group 18: He, Ne, Ar, Kr, Xe, Rn. (Og had not yet been named when the 2005 IUPAC Red Book was published, and its chemical properties are not yet experimentally known.)
- Lanthanoids – Elements 57–71: La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu.
- Actinoids – Elements 89–103: Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr.
- Rare-earth metals – Sc, Y, plus the lanthanoids.
- Transition elements – Elements in groups 3 to 11 or 3 to 12.
Another common classification is by degree of metallic – metalloidal – nonmetallic behaviour and characteristics. There is no general agreement on the name to use for these sets: in this English Wikipedia, the name used is "category". Very often these categories are marked by a background color in the periodic table. Category names used here, without any claim to universality, are:
- Alkali metals, alkaline earth metals, and noble gases: Same as the IUPAC system above.
- Transition elements are instead referred to as transition metals.
- Lanthanoids and actinoids are instead referred to as lanthanides and actinides respectively.
- Rare-earth elements, pnictogens, chalcogens, and halogens are not used as category names, but the latter three are valid as group (column) names.
- Additional element category names used:
- Post-transition metals – The metals of groups 12–17: Zn, Cd, Hg, Al, Ga, In, Tl, Sn, Pb, Bi, Po. The period 7 elements Nh, Fl, Mc, Lv, and Ts are additionally predicted to be post-transition metals.
- Metalloids – Elements with properties intermediate between metals and non-metals: B, Si, Ge, As, Sb, Te, At.
- Reactive nonmetals – Nonmetals that are chemically active (as opposed to noble gases): H, C, N, P, O, S, Se, F, Cl, Br, I
- Superactinides – Hypothetical series of elements 121 to 157, which includes a predicted "g-block" of the periodic table.
Many other names for sets of elements are in common use, and yet others have been used throughout history. These sets usually do not aim to cover the whole periodic table (as for example period does). Some examples:
- Precious metals – Variously-defined group of non-radioactive metals of high economical value.
- Coinage metals – Various metals used to mint coins, primarily the group 11 elements Cu, Ag, and Au.
- Platinum group – Ru, Rh, Pd, Os, Ir, Pt.
- Noble metal – Variously-defined group of metals that are generally resistant to corrosion. Usually includes Ag, Au, and the platinum-group metals.
- Heavy metals – Variously-defined group of metals, on the base of their density, atomic number, or toxicity.
- Native metals – Metals that occur pure in nature, including the noble metals and others such as Sn and Pb.
- Earth metal – Old historic term, usually referred to the metals of groups 3 and 13, although sometimes others such as beryllium and chromium are included as well.
- Transuranium elements – Elements with atomic number greater than 92.
- Transactinide elements – Elements after the actinides (atomic number greater than 103).
- Transplutonium elements – Elements with atomic number greater than 94.
- Minor actinides – Actinides found in significant quantities in nuclear fuel, other than U and Pu: Np, Am, Cm.
- Heavy atom – term used in computational chemistry to refer to any element other than hydrogen and helium.
- ^ International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSC–IUPAC. ISBN 0-85404-438-8. Electronic version. Retrieved 10 June 2012.
External links Periodic table
The periodic table, also known as the periodic table of elements, is a tabular display of the chemical elements, which are arranged by atomic number, electron configuration, and recurring chemical properties. The structure of the table shows periodic trends. The seven rows of the table, called periods, generally have metals on the left and non-metals on the right. The columns, called groups, contain elements with similar chemical behaviours. Six groups have accepted names as well as assigned numbers: for example, group 17 elements are the halogens; and group 18 are the noble gases. Also displayed are four simple rectangular areas or blocks associated with the filling of different atomic orbitals.
The organization of the periodic table can be used to derive relationships between the various element properties, and also to predict chemical properties and behaviours of undiscovered or newly synthesized elements. Russian chemist Dmitri Mendeleev published the first recognizable periodic table in 1869, developed mainly to illustrate periodic trends of the then-known elements. He also predicted some properties of unidentified elements that were expected to fill gaps within the table. Most of his forecasts proved to be correct. Mendeleev's idea has been slowly expanded and refined with the discovery or synthesis of further new elements and the development of new theoretical models to explain chemical behaviour. The modern periodic table now provides a useful framework for analyzing chemical reactions, and continues to be widely used in chemistry, nuclear physics and other sciences.
The elements from atomic numbers 1 (hydrogen) through 118 (oganesson) have been discovered or synthesized, completing seven full rows of the periodic table. The first 94 elements all occur naturally, though some are found only in trace amounts and a few were discovered in nature only after having first been synthesized. Elements 95 to 118 have only been synthesized in laboratories or nuclear reactors. The synthesis of elements having higher atomic numbers is currently being pursued: these elements would begin an eighth row, and theoretical work has been done to suggest possible candidates for this extension. Numerous synthetic radionuclides of naturally occurring elements have also been produced in laboratories.
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