Chemistry Nexus

by WebElements: the periodic table on the web

Cold working of sodium metal converts body centred sodium metal to a mixture of a hexagonal form and body centred sodium at 5 K. The hexagonal from converts back to the body-centred form at 100-100 K.Cold working of lithium metal converts body centred lithium metal to a mixture of a hexagonal form and body centred lithium at 78 K.

Potassium, rubidium, and caesium retain their body centred structure after cooling.

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December 24th, 2009

Posted In: Chemistry, Crystallography, Group 1 elements

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Lithium at room temperature is body-centered cubic with 2 atoms per unit cell. The lattice constant for lithium metal is 3.51004 ± 0.00041 Å at 25°C. The theoretical density is 533 kg m–3 and the Li—Li bond distance for coordination number 8 is 3.0398 Å.1

SMILES: [Li]InChI: InChI=1/Li

References

1. Nadler, M. R., and C. P. Kempier. 1959. “Crystallographic Data 186.
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December 24th, 2009

Posted In: Chemistry, Crystallography, Group 1 elements

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Uranium nitride, UN, is available through the direct reaction of uranium metal and nitrogen. The crystal structure is the NaCl type.

Abstract1

Crystal structure of uranium nitride, UN. The structure is face-centered cubic with a lattice constant of 4889 ± 0.001 Å at 26°C and sodium chloride type. The theoretical density is 14315 kg m–3, and the U—N bond distance for coordination number 6 is 2.4449 Å.

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December 24th, 2009

Posted In: Chemistry, Crystallography

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Helium (He)In a letter to Nature E. Kim and M. H. W. Chan (Pennsylvania State University, USA) note that when liquid 4He is cooled below 2.176 K, it undergoes a phase transition and becomes a superfluid with zero viscosity. They claim that in addition to superflow in the liquid phase, superflow can also occur under some conditions in the solid phase of one of the helium isotopes (4He), and present results to back this up.

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December 19th, 2009

Posted In: Chemistry

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Attempts have been made at GSI to make element 120 (unbinilium). Several new elements have been made at GSI in the last few years. However after 120 days no decay chain of element 120 was found. With the total number of 2.6 × 1019 projectiles which impinged upon the target, it deduced that the stability in the region around Z=120, N=184 is not exceptionally high with respect to the neighbouring regions.

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December 17th, 2009

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The results of cross-section measurements for the reactions 209Bi(12C,X)Au, E=4.8 and 25.2 GeV and 209Bi(20Ne,X)Au, E=8.0 GeV are reported. The observed yields of the gold isotopes show a similar dependence on mass number for each reaction, differing slightly in the position of the centroid of the distribution. As the projectile energy increases, the inferred excitation energy of the primary residues remains the same or decreases slightly.

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December 17th, 2009

Posted In: Chemistry, Nuclear chemistry

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ScCl3, TiCl3 und VCl3 kristallisieren hexagonal-rhomboedrisch in dem gleichen Gitter wie FeCl3 (DO5-Typ).

The trichlorides ScCl3, TiCl3 and VCl3 crystallise hexagonal-rhombohedral in the same system as FeCl3 (DO5-type )1

References

1. Klemm, Wilhelm, and Ehrhard Krose. “Die Kristallstrukturen von ScCl3, TiCl3 und VCl3“, Z.
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December 16th, 2009

Posted In: Chemistry

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The positions of the elements La, Ac, Lu, and Lr in the WebElements periodic table is justified eloquently in the article by William B. Jensen.1

Abstract:1 The debate as to whether lanthanum and actinium or lutetium and lawrencium should be placed in group IIIB of the periodic table along with scandium and yttrium has along but poorly publicized history.

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December 16th, 2009

Posted In: Chemistry

The giant gypsum crystals in Mexico’s “Cueva de los Cristales” are a stunning natural wonder featuring crystals up to 11 metres long.

gypsum

These giant gypsum (hydrated calcium sulphate) crystals in the “Cave of Crystals” in the Naica mine, Chihuahua, Mexico pose an interesting problem: how are they formed. A Spanish-Mexican team led by Prof García-Ruiz et al. propose that these crystals are derived from “a self-feeding mechanism driven by a solution-mediated, anhydrite-gypsum phase transition”.

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December 15th, 2009

Posted In: Chemistry

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A New Chemical Element in the Periodic Table

A New Chemical Element in the Periodic Table

In honour of scientist and astronomer Nicolaus Copernicus (1473-1543), the discovering team around Professor Sigurd Hofmann suggested the name copernicium with the element symbol Cp (eventually the symbol Cn was accepted) for the new element 112, discovered at the GSI Helmholtzzentrum für Schwerionenforschung (Center for Heavy Ion Research) in Darmstadt. It was Copernicus who discovered that the Earth orbits the Sun, thus paving the way for our modern view of the world.

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December 15th, 2009

Posted In: Chemistry, Nuclear chemistry

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