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Carbides of the actinide elements, which have stoichiometry MC < sub > 2 </ sub > and M < sub > 2 </ sub > C < sub > 3 </ sub >, are also described as salt-like derivatives of C < sub > 2 </ sub >< sup > 2 –</ sup >.
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Carbides and <
Carbides also form upon high temperature treatment of Cr < sub > 2 </ sub > O < sub > 3 </ sub > with carbon.
Carbides and are
Carbides of silicon, tungsten, boron and titanium, are among the hardest known materials, and are used as abrasives in cutting and grinding tools.
Carbides are binary compounds of carbon with an element that is less electronegative than it.
Carbides and salt-like
Carbides can be generally classified by chemical bonding type as follows: ( i ) salt-like, ( ii ) covalent compounds, ( iii ) interstitial compounds, and ( iv ) " intermediate " transition metal carbides.
actinide and elements
Actinium gave the name to the actinide series, a group of 15 similar elements between actinium and lawrencium in the periodic table.
The actinide or actinoid ( IUPAC nomenclature ) series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.
All but one of the actinides are f-block elements, corresponding to the filling of the 5f electron shell ; lawrencium, a d-block element, is also generally considered an actinide.
It is an actinide element, the sixth transuranium element to be synthesized, and has the second-highest atomic mass of all the elements that have been produced in amounts large enough to see with the unaided eye ( after einsteinium ).
Other isotopes are synthesized in various laboratories, but at much smaller amounts, by bombarding heavy actinide elements with light ions.
In the periodic table of the elements, it is a period 7 d-block element and the last element of the actinide series.
Researchers have shown that mendelevium has a moderately stable dipositive ( II ) oxidation state in addition to the more characteristic ( for actinide elements ) tripositive ( III ) oxidation state, the latter being the more dominantly exhibited state in an aqueous solution ( chromatography being the process used ).
Among the heavy actinide elements, however, those isotopes that have an odd number of neutrons ( such as U-235 with 143 neutrons ) bind an extra neutron with an additional 1 to 2 MeV of energy over an isotope of the same element with an even number of neutrons ( such as U-238 with 146 neutrons ).
* Minor actinides ( MA ), the actinide elements in used nuclear fuel other than uranium and plutonium
The first superdeformed states to be observed were the fission isomers, low-spin states of elements in the actinide and lanthanide series.
Extended to a lattice of magnetic impurities, the Kondo effect likely explains the formation of heavy fermions and Kondo insulators in intermetallic compounds, especially those involving rare earth elements like cerium, praseodymium, and ytterbium, and actinide elements like uranium.
The known elements most susceptible to spontaneous fission are the synthetic high-atomic-number actinide elements with odd atomic numbers: mendelevium and lawrencium, and also some of the transactinide very-heavy elements, such as rutherfordium.
Seaborg's actinide concept of heavy element electronic structure, predicting that the actinides form a transition series analogous to the rare earth series of lanthanide elements, is now well accepted in the scientific community and included in all standard configurations of the periodic table.
The actinide series are the second row of the f-block ( 5f series ) and comprise the elements from Actinium to Lawrencium.
Seaborg's subsequent elaborations of the actinide concept theorized a series of superheavy elements in a transactinide series comprising elements 104 through 121 and a superactinide series inclusive of elements 122 through 153.
Examples are elements found in the lanthanide and actinide series.
The spent nuclear fuel to which this process is applied consists primarily of certain very high atomic-weight ( actinoid or " actinide ") elements ( e. g., uranium ) along with smaller amounts of material composed of lighter atoms, notably the so-called fission products.
Transactinide elements are also transuranic elements, that is, have an atomic number greater than that of uranium ( 92 ), an actinide.
actinide and which
In the periodic table, it is located to the right of the actinide curium, to the left of the actinide californium and below the lanthanide terbium with which it shares many similarities in physical and chemical properties.
which is the largest strain in any actinide compound.
The search for element 93 in minerals was encumbered by the fact that the predictions on the chemical properties of element 93 were based on a periodic table which lacked the actinide series, and therefore placed thorium below hafnium, protactinium below tantalum, and uranium below tungsten.
As the production of radioactive atoms by the ISOL technique depends on the free atom chemistry of the element to be studied, there are certain beams which cannot be produced by simple proton bombardment of thick actinide targets.
By neutron capture and two successive beta decays, becomes plutonium-239 (), which, by successive neutron capture, becomes plutonium-240 (), plutonium-241 (), plutonium-242 () and ( after further beta decays ) other transuranic or actinide nuclides.
Buildup of heavy actinides in current thermal-neutron fission reactors, which cannot fission actinide nuclides that have an even number of neutrons.
* Much cleaner: as a full recycle system, the discharge wastes from the reactor are predominately fission products, most of which have relatively short half lives compared to longer-lived actinide wastes.
Chemistry Nobelist Glenn T. Seaborg who first proposed the actinide concept which led to the acceptance of the actinide series also proposed the existence of a transactinide series ranging from element 104 to 121 and a superactinide series approximately spanning elements 122 to 153.
actinide and have
Further experiments have demonstrated an actinide chemistry for the new element, so by 1970 it was known that lawrencium is the last actinide.
We're looking at reactors that have a high-energy neutron spectrum that can actually allow you to burn down the long-lived actinide waste.
The rare earth oxides ( cerium ) and actinide ( thorium ) in the mantle have a low emissivity in the infrared ( in comparison with an ideal black body ), but have high emissivity in the visible spectrum.
" Despite the million-fold reduction in radiotoxicity offered by this scheme, some believe that actinide removal would offer few if any significant advantages for disposal in a geologic repository because some of the fission product nuclides of greatest concern in scenarios such as groundwater leaching actually have longer half-lives than the radioactive actinides.
Unlike reactors that use relatively slow low energy ( thermal ) neutrons, fast neutron reactors need nuclear reactor coolant that does not moderate or block neutrons ( like water does in an LWR ) so that they have sufficient energy to fission actinide isotopes that are fissionable but not fissile.
actinide and <
A number of actinide compounds are ferromagnets at room temperature or become ferromagnets below the Curie temperature ( T < sub > C </ sub >).
PuP is one actinide pnictide that is a paramagnet and has cubic symmetry at room temperature, but upon cooling undergoes a lattice distortion to tetragonal when cooled to below its T < sub > c </ sub > = 125 K. PuP has an easy axis of < 100 >, so that
actinide and M
* Morss, L. R., Edelstein, N. M., Fuger, J., The chemistry of the actinide and transactinide element, 3, ( 2006 ), 1630 – 1636
actinide and C
Californium is a silvery white actinide metal with a melting point of 900 ± 30 ° C and an estimated boiling point of 1745 ° C.
actinide and 3
The actinide series derives its name from the group 3 element actinium.
actinide and are
This led to americium being located right below its twin lanthanide element europium ; it was thus by analogy named after another continent, America: " The name americium ( after the Americas ) and the symbol Am are suggested for the element on the basis of its position as the sixth member of the actinide rare-earth series, analogous to europium, Eu, of the lanthanide series.
The second important berkelium isotope, berkelium-247, is an alpha-emitter, as are most actinide isotopes.
Although lutetium and lawrencium are in the d-block, they are not considered transition metals but a lanthanide and an actinide, respectively, according to IUPAC.
There are two main types of breeding cycles, and they can both reduce actinide wastes:
The two stages of extraction are used to improve the purity of the actinide product, the organic phase used for the first extraction will suffer a far greater dose of radiation.
With fast neutrons, the ratio between splitting and the capture of neutrons of plutonium or minor actinide is often larger than when the neutrons are slower, at thermal or near-thermal " epithermal " speeds.
Also if some actinide materials such as Cf or spent nuclear fuel are used within the hotcell then a layer of water or polyethylene may be needed to lower the neutron dose rate.
1.459 seconds.