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A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
However there are numerous exceptions; for example the lightest exception is chromium, which would be predicted to have the configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 4 4s 2, written as [Ar] 3d 4 4s 2, but whose actual configuration given in the table below is [Ar] 3d 5 4s 1.
Og, 118, oganesson : 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 6 7s 2 5f 14 6d 10 7p 6 Note that these electron configurations are given for neutral atoms in the gas phase, which are not the same as the electron configurations for the same atoms in chemical environments.
Each distinct atomic number therefore corresponds to a class of atom: these classes are called the chemical elements. [5] The chemical elements are what the periodic table classifies and organizes. Hydrogen is the element with atomic number 1; helium, atomic number 2; lithium, atomic number 3; and so on.
This is a list of chemical elements and their atomic properties, ordered by atomic number (Z). Since valence electrons are not clearly defined for the d-block and f-block elements, there not being a clear point at which further ionisation becomes unprofitable, a purely formal definition as number of electrons in the outermost shell has been used.
Thus element 164 with 7d 10 9s 0 is noted by Fricke et al. to be analogous to palladium with 4d 10 5s 0, and they consider elements 157–172 to have chemical analogies to groups 3–18 (though they are ambivalent on whether elements 165 and 166 are more like group 1 and 2 elements or more like group 11 and 12 elements, respectively). Thus ...
5: Rubidium 37 Rb 85.468: Strontium 38 Sr 87.62: Yttrium 39 Y 88.906: Zirconium 40 Zr 91.224: Niobium 41 Nb 92.906: Molybdenum 42 Mo 95.95: Technetium 43 Tc [97] Ruthenium 44 Ru 101.07: Rhodium 45 Rh 102.91: Palladium 46 Pd 106.42: Silver 47 Ag 107.87: Cadmium 48 Cd 112.41: Indium 49 In 114.82: Tin 50 Sn 118.71: Antimony ...
The following table give predictions for the crystalline structure of elements 85–87, 100–113 and 118; all but radon [2] have not been produced in bulk. Most probably Cn and Fl would be liquids at STP (ignoring radioactive self-heating concerns).