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Five more elements that were first created artificially are strictly speaking not synthetic because they were later found in nature in trace quantities: 43 Tc, 61 Pm, 85 At, 93 Np, and 94 Pu, though are sometimes classified as synthetic alongside exclusively artificial elements. [2] The first, technetium, was created in 1937. [3]
Meitnerium is a synthetic chemical element; it has symbol Mt and atomic number 109. It is an extremely radioactive synthetic element (an element not found in nature, but can be created in a laboratory).
At high pressure formation of TcH 1.3 from elements was also reported. [33] TcCl 4 forms chain-like structures, similar to the behavior of several other metal tetrachlorides. The following binary (containing only two elements) technetium halides are known: TcF 6, TcF 5, TcCl 4, TcBr 4, TcBr 3, α-TcCl 3, β-TcCl 3, TcI 3, α-TcCl 2, and β-TcCl 2.
Metals are not the only type of chemical element that can occur in the native state. Non-metallic elements occurring in the native state include carbon, sulfur, and selenium. Silicon, a semi-metal, has rarely been found in the native state as small inclusions in gold. [4]
As a synthetic element, it is not found in nature and can only be made in a particle accelerator. It is radioactive; the most stable known isotope, 267 Rf, has a half-life of about 48 minutes. In the periodic table, it is a d-block element and the second of the fourth-row transition elements. It is in period 7 and is a group 4 element.
The free element is not found in nature, but niobium occurs in combination with other elements in minerals. [40] Minerals that contain niobium often also contain tantalum. Examples include columbite ( (Fe,Mn)Nb 2 O 6 ) and columbite–tantalite (or coltan , (Fe,Mn)(Ta,Nb) 2 O 6 ). [ 47 ]
Sodium is a chemical element; it has symbol Na (from Neo-Latin natrium) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable isotope is 23 Na. The free metal does not occur in nature and must be prepared from compounds.
Rhenium is probably not found free in nature (its possible natural occurrence is uncertain), but occurs in amounts up to 0.2% [35] in the mineral molybdenite (which is primarily molybdenum disulfide), the major commercial source, although single molybdenite samples with up to 1.88% have been found. [43]