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Symbol Hm
Atomic number 170
Pronunciation /'helm•hōl•tzē•(y)üm/
Named after Hermann von Helmholtz
Name in Saurian Xocmxeckjaim (Xm)
Systematic name Unseptnilium (Usn)
Location on the periodic table
Group 16
Period 8
Family Oxygen family (Chalcogens)
Series Kirchoffide series
Coordinate 8p4
Element above Helmholtzium Livermorium
Element left of Helmholtzium Joulium
Element right of Helmholtzium Bunsenine
Atomic properties
Subatomic particles 665
Atomic mass 499.1464 u, 828.8520 yg
Atomic radius 141 pm, 1.41 Å
Covalent radius 135 pm, 1.35 Å
van der Waals radius 187 pm, 1.87 Å
Nuclear properties
Nucleons 495 (170 p+, 325 no)
Nuclear ratio 1.91
Nuclear radius 9.45 fm
Half-life 12.508 ms
Decay mode Spontaneous fission
Decay product Various
Electronic properties
Electron notation 170-9-26
Electron configuration [Og] 5g18 6f14 7d10 8s2 8p4 9s2 9p2
Electrons per shell 2, 8, 18, 32, 50, 32, 18, 6, 4
Oxidation states +2, +4, +6, +8
(an amphoteric oxide)
Electronegativity 2.33
First ionization energy 896.2 kJ/mol, 9.288 eV
Electron affinity 154.2 kJ/mol, 1.598 eV
Physical properties
Bulk properties
Molar mass 499.146 g/mol
Molar volume 29.441 cm3/mol
Density 16.954 g/cm3
Atomic number density 1.21 × 1021 g−1
2.05 × 1022 cm−3
Average atomic separation 366 pm, 3.66 Å
Speed of sound 10687 m/s
Magnetic ordering Diamagnetic
Crystal structure Base-centered monoclinic
Color Black
Phase Solid
Thermal properties
Melting point 672.23 K, 1210.01°R
399.08°C, 750.34°F
Boiling point 1331.56 K, 2396.80°R
1058.41°C, 1937.13°F
Liquid range 659.33 K, 1186.79°R
Liquid ratio 1.98
Triple point 672.27 K, 1210.08°R
399.12°C, 750.41°F
@ 66.154 Pa, 0.49619 torr
Critical point 2170.90 K, 3907.62°R
1897.75°C, 3447.95°F
@ 9.4147 MPa, 92.917 atm
Heat of fusion 7.270 kJ/mol
Heat of vaporization 124.117 kJ/mol
Heat capacity 0.05019 J/(g•K), 0.09034 J/(g•°R)
25.052 J/(mol•K), 45.093 J/(mol•°R)
Abundance in the universe
By mass Relative: 1.29 × 10−35
Absolute: 4.32 × 1017 kg
By atom 6.79 × 10−37

Helmholtzium is the provisional non-systematic name of a theoretical element with the symbol Hm and atomic number 170. Helmholtzium was named in honor of Hermann von Helmholtz (1821–1894), who worked on the conservation of energy. This element is known in the scientific literature as unseptnilium (Usn), dvi-polonium, or simply element 170. Helmholtzium is the heaviest chalcogen and is the fourth member of the kirchoffide series, placing this element at 8p4 coordinate on the periodic table.

Atomic properties Edit

After filling first four electrons in the ninth shell, there are two filling in the eighth shell in the 8p3/2 orbital. Helmholtzium contains 170 electrons overall in 26 orbitals surrounding the nucleus, where it contains almost all of atom's mass and where most of the component particles reside. The nucleus contains 495 particles
–– 170 protons and 325 neutrons. Helmholtzium atom masses 499.15 daltons, with 99.98% of it is concentrated in its nucleus.

Isotopes Edit

Like every other element heavier than lead, helmholtzium has no stable isotopes. The longest-lived isotope is 495Hm with a half-life of 12.5 milliseconds. It undergoes spontaneous fission, splitting into three lighter nuclei plus neutrons like the example.

Hm → 208
Pb + 159
Tb + 51
V + 77 1

As with other elements, helmholtzium has meta states, which are excited states of isotopes. The most stable is 497mHm with a half-life of 470 milliseconds, while the second most stable is 499mHm with a half-life of 334 milliseconds.

Chemical properties and compounds Edit

Helmholtzium is assumed to behave chemically like livermorium and polonium, but because its electron configuration is unique relative to lighter cogeners due to relativistic effects, it may not behave like lighter cogeners. Though based on its electronegativity and first ionization energy, helmholtzium would behave chemically like family members selenium and tellurium, and this element would be placed between Se and Te in the reactivity series. The two electrons in the 8p3/2 orbital and four in the ninth shell participitate well in bonding and its most common oxidation state is +6 (hexavalent), with +2 (divalent), +4 (tetravalent), and +8 (octavalent) being less common. However, when dissolving, it most commonly forms +2 ions (colorless), followed by +4 (pink), +6 (peach), then +8 (maroon).

This element can involve in complex anions, such as HmF6−
, HmO2−
, HmH4−
, HmS4−
, and HmCl8−

Helmholtzium would slowly react with fluorine to form helmholtzium hexafluoride (HmF6), reacts with chlorine to form helmholtzium hexachloride (HmCl6), bromine to form helmholtzium tetrabromide (HmBr4), and iodine to form helmholtzium tetraiodide (HmI4). Because there are different oxistates, it can form different species of corresponding halides, like HmF8, HmF4, HmCl4, HmCl2, HmBr2, and HmI2.

An extremely strong base helmholtzium hydroxide (Hm(OH)2) forms when molten helmholtzium reacts with steam, helmholtzium oxide (HmO2) is also formed as a byproduct. The byproduct then reacts with steam to form the most common oxide HmO3 like the equations.

2 Hm + 2 H2O + O2 → Hm(OH)2 + HmO2 + H2
HmO2 + H2O → HmO3 + H2

Helmholtzium can form compounds besides oxides, hydroxide, and halides. Helmholtzium hexahydride (HmH6) is a colorless gas that has a tar-like smell with a condensation point of −20°C and solidifying at −38°C. Helmholtzium disulfide (HmS2) and trisulfide (HmS3) are both light brown powder, though at a little different hues between the two with HmS2 being slightly darker. Helmholtzium dinitride (HmN2) is a lemon yellow powder. Helmholtzium can even form many species of borides, like HmB2, HmB36, and even HmB126.

This black substance can form organic compounds, called organohelmholtzium. An example is tetraethylhelmholtzium ((C2H5)4Hm), as well as simpler diethylhelmholtzium ((C2H5)2Hm).

Physical properties Edit

Helmholtzium is a soft, brittle black metal that melts to a black, tar-like liquid. But first it got to be heated to 399°C and needs to absorb 7.27 kJ/mol of energy in order to become a liquid. Formation of dark gray vapor would require lot more energy, at 124.12 kJ/mol and be heated even more to 1058°C in order for its vapor pressure to equal ambient pressure. If we decrease the ambient pressure, the boiling point would decrease until it reaches the melting point. This point is called the triple point. For helmholtzium, it is almost identical to its melting point in temperature but at a pressure of 66.15 Pa, just 11532 the atmospheric pressure on Earth at sea level and 110.4 the atmospheric pressure on Mars.

In the solid form, there are two allotropes: black powder and black crystals. The crystalline form has a base-centered monoclinic crystal lattice. Helmholtzium's density is approaching 17 g/cm3 and sound travels through it quite fast, approaching 10700 m/s, nearly three times faster than average speed for an element.

Allotropes Edit

Helmholtzium has couple of allotropes. A black amorphous solid forms upon quick solidifcation, while slow solidification can allow black crystals to form. Not all helmholtzium are black, purple helmholtzium also exists as crystalline solid, amorphous solid, or even a liquid.

Occurrence Edit

It is almost certain that helmholtzium doesn't exist on Earth at all, but it is believe to barely exist somewhere in the universe due to its brief lifetime. Every element heavier than iron can only naturally be produced by exploding stars. But it is likely 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 hyperheavy element. In the universe, only advanced technological civilizations can produce this element, but barely because it requires so much energy to produce this element, thus it is so unstable. An estimated abundance of helmholtzium in the universe by mass is 1.29 × 10−35, which amounts to 4.32 × 1017 kilograms.

Synthesis Edit

To synthesize most stable isotopes of helmholtzium, nuclei of a couple lighter elements must be fused together, and right amount of neutrons must be seeded. This operation would be impossible using current technology since it requires a tremendous amount of energy, thus its cross section would be so low that it is beyond the technological limit. Even if synthesis succeeds, this resulting element would immediately undergo fission. Here's couple of example equations in the synthesis of the most stable isotope, 495Hm.

Gd + 137
Ba + 120
Sn + 80 1
n → 495
No + 166
Er + 68 1
n → 495
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
1 H He
2 Li Be B C N O F Ne
3 Na Mg Al Si P S Cl Ar
4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
6 Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
7 Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Tn Og
8 Nw G * Du Sh Hb Da Bo Fa Av So Hr Wt Dr Le Vh Hk Ke Ap Vw Hu Fh Ma Kp Gb Bc Hi Kf Bn J Hm Bs Rs
* Ls Dm Ms Ts Dt Mw Pk By Bz Fn Dw To Pl Ah My Cv Fy Ch A Ed Ab Bu

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