|Name in Saurian|| Conajaim (Co)|
|Systematic name|| Unpentquadium (Upt)|
|Location on the periodic table|
|Above element||Nobelium (102No)|
|Previous element||Diracium (153Dr)|
|Next element||Vanthoffium (155Vh)|
|Atomic mass||440.6572 u, 731.7285 yg|
|Atomic radius||124 pm, 1.24 Å|
|Van der Waals radius||179 pm, 1.79 Å|
|Nucleons||437 (154 p+, 283 n0)|
|Nuclear radius||9.07 fm|
|Electron configuration|| [Mc] 5g18 6f12 7d2 8s2 8p2|
2, 8, 18, 32, 50, 30, 10, 4
|Oxidation states|| 0, +1, +2|
(mildly basic oxide)
|First ionization energy||1257.8 kJ/mol, 13.036 eV|
|Electron affinity||8.5 kJ/mol, 0.088 eV|
|Covalent radius||133 pm, 1.33 Å|
|Molar mass||440.657 g/mol|
|Molar volume||31.275 cm3/mol|
|Atomic number density||1.93 × 1022 cm−3|
|Average atomic separation||373 pm, 3.73 Å|
|Speed of sound||2087 m/s|
|Crystal structure||Simple hexagonal|
|Melting point|| 1744.63 K, 1471.48°C|
|Boiling point|| 3100.70 K, 2827.55°C|
|Liquid range||1356.07 K/°C, 2440.93°F/°R|
|Triple point|| 1744.63 K, 1471.48°C|
@ 5.5324 Pa, 0.041496 torr
|Critical point|| 7282.94 K, 7009.79°C|
@ 177.9524 MPa, 1756.259 atm
|Heat of fusion||18.441 kJ/mol|
|Heat of vaporization||301.193 kJ/mol|
|Heat capacity|| 0.05048 J/g/K, 0.09087 J/g/°R|
22.245 J/mol/K, 40.041 J/mol/°R
|Universe (by mass)|| Relative: 7.67 × 10−37|
Absolute: 2.57 × 1016 kg
Lewisium is the fabricated name of a hypothetical element with the symbol Le and atomic number 154. Lewisium was named in honor of Gilbert N. Lewis (1875–1946), who discovered covalent bond, reformulate chemical dynamics, and developed theory of Lewis acids and bases; he also coined "photon" and explained phosphorescence. This element is known in scientific literature as unpentquadium (Upq), eka-nobelium, or simply element 154. Lewisium is the last member of the dumaside series, found in the third row of f-block (below ytterbium and nobelium); this element is located in periodic table coordinate 6f14.
Lewisium is a shiny pale peach metal that does not darken when exposed to air; it is ductile and malleable twice as dense as zinc with a value of over 14 g/cm3. Lewisium atoms together form hexagonal crystal lattices that upon heating it transforms to face centered cubic at 479°C and to body centered cubic at 901°C. Atoms that make up lattices are separated by an average of 373 pm from each other.
Lewisium liquifies at 1471°C (heat of fusion: 18.44 kJ/mol) and vaporizes at 2828°C (heat of vaporization: 301.19 kJ/mol). Its corresponding liquid range is 1.78, obtained by dividing these two values but they have to be converted to kelvins by adding 273 to each number first since Celsius scale is not the absolute temperature scale. Because the boiling point depends on pressure, different pressure would result in different boiling point so is liquid ratio. If ambient pressure is lower, its boiling point would correspondingly be lower. If pressure is low enough, boiling point would equal its melting point, called its triple point, this occurs at a pressure of 5.53 Pa, only 1⁄18300 of that of Earth's sea level pressure and 0.87% the atmospheric pressure on Mars. The critical point is on the opposite corner of the phase diagram as its triple point; for lewisium, this occurs at 7010°C under a 178 MPa pressure, 1756 times greater than Earth's and 19 times the surface pressure on Venus.
Lewisium atom has 24 orbitals in 8 shells of 154 electrons surrounding the nucleus containing 437 nucleons and a 1.84 ratio (154 protons, 283 neutrons). Since lewisium marks the last element of the f-block series, the f-orbital should be filled with 14 electrons, but due to spin-orbit coupling due to relativistic effects, there are just 12 and it needs two more. Instead there are two in the d-orbital one beyond the shell where occupying f-orbital is.
Like every other elements heavier than lead, lewisium has no stable isotopes. The most stable isotope is 437Le with a half-life of 53.6 seconds. It undergoes spontaneous fission, splitting into two or three lighter nuclei as well as neutrons like the following examples.
437Le is the only isotope with half-life longer than one second as every other isotope have half-lives less than 400 milliseconds.
Lewisium is a noble metal, which means it is a very unreactive metal, even less reactive than gold. It is considered the least reactive element. The most common oxidation state is obviously zero, while +1 and +2 are less common. The lack of reactivity is due to filled g- and f-orbitals as well as full p1/2 orbital. The electronegativity on the Pauling scale is 2.98 while the first ionization energy is 13.4 eV, much higher than lighter cogener nobelium (6.65 eV). Such a high electronegativity means it can accept electrons from other atoms but it can't because of the energy shielding effect caused by incompleted f-orbital. It can form metal-nonmetal covalent bonds like is typical of internonmetallic compounds, instead of polar or ionic bonds typical of metal-nonmetal compounds.
There are interesting compounds of lewisium, such as lewisium(II) oxide (LeO), which is a dark yellow crystalline substance, and lewisium(II) carbide (Le2C), which has the melting point of 5318°C (9604°F), just below the surface temperature of our Sun. Lewisium halides include LeF, LeF2, LeCl, and LeCl2, all of which are white ionic solids except for LeCl2, which is pale yellow.
Occurrence and synthesis Edit
It is almost certain that lewisium doesn't exist on Earth at all, but it is believed to exist somewhere in the universe, at least in very tiny amounts. Since every element heavier than lithium were produced by stars, then lewisium must be produced in stars, and then thrown out into space by exploding stars. But it is theoretically impossible for even the most powerful supernovae or most violent neutron star collisions to produce this element through r-process because there's not enough energy available or not enough neutrons, respectively, to produce this heavy element. Instead, this element virtually can only be made by advanced technological civilizations. An estimated abundance of lewisium in the universe by mass is 7.67 × 10−37, which amounts to 2.57 × 1016 kilograms.
To go along with other such civilizations, humans on Earth may eventually have the capability to synthesize lewisium. To synthesize most stable isotopes of lewisium, nuclei of a couple lighter elements must be fused together, and right amount of neutrons must be seeded. This operation would be extremely difficult since it requires vast amounts of energy and even if nuclei of this element were produced would immediately decay due to its brief half-life. Here's couple of example equations in the production of the most stable isotope 437Le.