Structure, Density

Atomic positions (Th based on X-ray [1] and N atoms based on neutron diffraction data [2])  

The atomic configuration in the hexagonal unit cell is illustrated in Fig. 5. The Th atoms have the close-packed configuration ABABCBCACA. .. observed in the samarium metal structure and the c axis is 9 times the separation of the hexagonal layers. The N(I) atoms 

The mean bond distances in this ionic compound are Th(Il)-4 N(l) = 235 and Th(I)-6N(ll) = 253 pm. The latter value is even larger than the bond distance Th-60 = 242.4 pm of Th with the coordination number of 8 in Th02 showing that the N ion radius is larger than that of the 0 ion by about 17 pm in these compounds, allowing for the difference in coordination [11]. 

Reported Hexagonal Lattice Parameters of Trigonal Th3N4 at Room Temperature. 

The Th3N4 structure is closely related to that of ThgNgO the unit cell of which is illustrated in Fig. 21, p. 67. The configuration about the Th(II) atoms of the Th3N4 structure is almost identical with that of Th in ThgNgO however, the Th(l) atoms form 6 bonds to N atoms, all occupying octahedral holes [1]. 

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Metal A lomic number Atomic weight Lattice structure Density at 20°C (g/em ) Melting point (°C) Thermal conductivity at 0-l00°C (W/m°C) Specific heat at 0°C (J/kg C) Coefficient of linear expansion at 20-iOO°C X 70 Thermal neutron cross-section (barns) (10-- m ) Resistivity at 0°C (fiil em) Temperature coefficient of resistance o-ioo°c X 10 ... 

ELEMENT CRYSTAL STRUCTURE DENSITY (g/ml) MELTING POINT (°Q HEAT OF vaporization (kcal/mole) ELECTRICAL CONDUCTIVITY (ohm-cm)r ... 

Calculate the atomic radius of each of the following elements from the data given (a) platinum, fee structure, density 21.450 g-cm 3 (b) tantalum, bcc structure, density 16.654 g-cm-3. 

The effects of the intramicellar confinement of polar and amphiphilic species in nanoscopic domains dispersed in an apolar solvent on their physicochemical properties (electronic structure, density, dielectric constant, phase diagram, reactivity, etc.) have received considerable attention [51,52]. hi particular, the properties of water confined in reversed micelles have been widely investigated, since it simulates water hydrating enzymes or encapsulated in biological environments [13,23,53-59]. 

Name Type Structure Density Viscosity Average ... 

Particle Identification Crystal Structure Density (g/cm3) Wt% Incorporation... 

Among various theories of electronic structure, density functional theory (DFT) [1,2] has been the most successful one. This is because of its richness of concepts and at the same time simplicity of its implementation. The new concept that the theory introduces is that the ground-state density of an electronic system contains all the information about the Hamiltonian and therefore all the properties of the system. Further, the theory introduces a variational principle in terms of the ground-state density that leads to an equation to determine this density. Consider the expectation value (H) of the Hamiltonian (atomic units are used)... 

Surface lattice structure Density of active surface atoms and reactivity of the surface determined by the crystalline orientation of silicon/electrolyte interface... 

Table XI gives the room-temperature, atmospheric pressure crystal structures, densities, and atomic volumes, along with the melting points and standard enthalpies of vaporization (cohesive energies), for the actinide metals. These particular physical properties have been chosen as those of concern to the preparative chemist who wishes to prepare an actinide metal and then characterize it via X-ray powder diffraction. The numerical values have been selected from the literature by the authors.

Actinide metal Crystal structure Density (g/cm ) Atomic volume (A ) Melting point (K) Enthalpy of vaporization AH, g (kJ/mol)... 

A study was made of relationships between compound rheological properties, microwave vulcanisation parameters and accelerators on the quality of extruded EPDM foam seals for the automotive industry. The influence of these factors on cell size and structure, density and mechanical properties was investigated. Correlations were found between the chemical composition of the compound, variations in processing parameters and the quality of the finished product. 12 refs. 

Golden yellow, soft and ductile metal body-centered cubic structure density 1.93 g/cm melts at 28.44°C vaporizes at 671°C vapor pressure 1 torr at 280°C electrical resistivity 36.6 microhm-cm (at 30°C) reacts with water dissolves in liquid ammonia forming a blue solution. 

Green hexagonal crystal system corundum type structure density 5.22 g/cm3 melts at 2,330°C vaporizes above 3,000°C insoluble in water and alcohol. 

Black cubic crystal zincblende structure density 5.775 g/cm melts at 525°C density of melt 6.48 g/mL dielectric constant 15.9 insoluble in water. 

Colorless needles tetragonal structure density 1.178 g/cm at 17.5°C melts around 375°C starts to decompose at 320°C decomposes at 400°C soluble in cold water decomposes in hot water sbghtly soluble in ethanol and bquid ammonia insoluble in benzene and ether. 

Silvery-white metal hexagonal close-packed structure density 9.84 g/cm melts at 1,663°C vaporizes at 3,402°C electrical resistivity 59 microhm-cm slightly paramagnetic thermal neutron cross section 108 barns soluble in acids. 

Silvery-white metal close-packed hexagonal structure density 1.74 g/cm at 20°C, 1.57 g/cm3 at 650 C (hquid melt) melts at 650 C vaporizes at 1,090°C vapor pressure 5 torr at 678 C and 20 torr at 763 C electrical resistivity 4.46 microhm-cm at 20 C, 28.0 microhm-cm at 650 C (hquid melt) surface tension 563 dynes/cm at 681 C modulus of elasticity 6.5x10 Ib/sq in Poisson s ratio 0.35 thermal neutron absorption cross section 0.059 bam soluble in dilute acids. 

Anhydrous magnesium sulfate is a white crystalline sohd occurring in alpha form as orthorhomic crystals or as a heta form having triclinic structure density 1.507 and 1.502 g/cm for alpha- and heta-forms, respectively decomposes at 323°C very soluble in water moderately soluble in methanol (5.25g/100 mL at 15°C). 

White tetragonal crystals rutile structure density 1.45 g/cm decomposes at 200°C reacts with water. 

White, shiny crystals orthogonal crystal structure density 1.96 g/cm sublimes at 150°C with decomposition vapor pressure 0.1 torr at 20°C insoluble in water soluble in benzene and paraffin od shghtly soluble in ether. 

Emerald-green crystals orthorhombic structure density 1.455 g/cm at 17°C melts at 230°C soluble in water, alcohol, chloroform, benzene and toluene insoluble in ether. 

Pale, yellow crystalline solid chlorine-like acrid odor monoclinic crystals having terahedral structure density 5.1 g/cm melts at 40.6°C vaporizes at 129.7°C sublimation begins below its boiling point vapor pressure 11 torr at 27°C critical temperature 405°C critical pressure 170 atm moderately soluble in water, 7.24 g/lOOmL at 25°C soluble in most organic solvents. 

Silvery-white metal face-centered cubic crystalline structure density 12.02 g/cm Vickers hardness, annealed 37-39 melts at 1,554°C vaporizes at 2,970°C electrical resistivity 9.93 microhm-cm at 0°C Poisson s ratio 0.39 magnetic susceptibility 5.231x10 cm /g thermal neutron cross section 8... 

Colorless transparent crystal or white powder monoclinic structure density 2.17 g/cm3 decomposes above 100°C soluble in water, 22.49 g/lOOml at 20°C, 60 g/lOOmI at 60°C pH of O.IM aqueous solution 8.2 practically insoluble in alcohol. 

Colorless crystals or white granular powder monochnic structure density 2.32 g/cm3 melts at 356°C decomposes at 400°C moderately soluble in cold water, 7.19 g/lOOmL at 20°C, solubility increasing with temperature, 57 g/lOOmL at 100°C insoluble in acetone and hquid ammonia. 

Colorless crystals or white powder monoclinic structure density 3.90 g/cm3 stable at ordinary temperatures melts at 560°C with partial decomposition, releasing oxygen moderately soluble in cold water 4.74 g/lOOmL at 0°C greater solubility in boiling water 32.3 g/lOOmL at 100°C soluble in potassium iodide solution insoluble in alcohol and liquid ammonia... 

Colorless transparent crystals or white granular or crystalline powder rhombohedral structure density 2.11 g/cm at 20°C melts at 334°C decomposes at 400°C evolving oxygen soluble in cold water, 13.3 g/lOOmL at 0°C highly soluble in boiling water, 247 g/lOOmL at 100°C lowers the temperature of water on dissolution very slightly soluble in ethanol soluble in glycerol and liquid ammonia. 

The monohydrate is a white crystalline solid monoclinic structure density 2.13 g/cm3 loses its water at about 160°C converts to carbonate when ignited effloresces in warm dry air soluble in water, 33 g/100 mL at 20°C a 0.05m solution of K2C2O4 2H2O has a pH 1.679. 

Colorless crystals or white crystalline powder rhomhohedral structure density 2.52 g/cm melts around 610°C under controlled conditions decomposes at 400°C slightly soluble in cold water 0.75 g/lOOmL at 0°C, soluble in boiling water, 21.8 g/lOOmL at 100°C practically insoluble in alcohol insoluble in ether. 

Colorless or white crystals trichnic structure density 2.477 g/cm stable in sohd crystalline form decomposes on heating, evolving oxygen completely decomposes at about 100°C sparingly soluble in cold water 1.75 g/lOOmL at 0°C moderately soluble at ordinary temperature, 5.29 g/100 mL at 20°C aqueous solution acidic and unstable, decomposing slowly at room temperature and more rapidly when the solution is warmed insoluble in alcohol. 

Shiny white metal with bright metaUic luster hard and malleable body-centered tetragonal structure density 15.37 g/cm (calculated) melts below 1,600 C vapor pressure 3.88x10-2 torr at about 1,930 C (calculated) superconducting below 1.4°K... 

Gray crystalline sohd or amorphous powder corundum-type structure density 8.20 g/cm decomposes at about 1,100 to 1,150°C insoluble in water, acids, or aqua regia. 

Hard silvery-white metal hexagonal close-packed crystal structure density 12.41 g/cm3 at 20°C melts at 2,334°C vaporizes at 4,150°C electrical resistivity 7.1 microhm-cm at 0°C hardness (annealed) 200-350 Vickers units Young s modulus 3.0x10 tons/in magnetic susceptibility 0.427 cm /g thermal neutron absorption cross section 2.6 barns insoluble in water, cold or hot acids, and aqua regia can be brought into aqueous phase by fusion of finely divided metal with alkaline hydroxides, peroxides, carbonates and cyanides. 

Greenish blue to black crystalline solid hexagonal or cubic crystals dia-mond-like structure density 3.217g/cm3 exceedingly hard, Mohs hardness 9.5 sublimes at about 2,700°C dielectric constant 7.0 electron mobility >100 cm /volt-sec hole mobility >20cm2/volt-sec band gap energy 2.8 eV insoluble in water and acids solubilized by fusion with caustic potash. 

Colorless crystals triclinic structure density 2.435g/cm3 at 13°C melts above 315°C decomposes on further heating soluble in water, 28.6 g/lOOmL at 25°C highly soluble in boiling water, lOOg/100 mL at 100°C aqueous solution strongly acidic, pH of 0.1 M solution 1.4 insoluble in liquid ammonia decomposed by alcohol into sodium sulfate and sulfuric acid... 

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