Noble Gas Configuration Research Articles

Polarizabilities of neutral atoms and atomic ions with a noble gas electron configuration.

Atomic polarizabilities play an important role in the development of force fields for molecular simulations, as well as for the development of qualitative concepts of atomic and molecular behavior. Coupled cluster theory at the coupled cluster singles doubles triples level with very large correlation-consistent basis sets with extended diffuse functions has been used to predict the polarizabilities of the atomic neutrals, mono-cations and mono-anions with a noble gas configuration. Additional corrections for scalar relativistic and spin-orbit effects were also included for the electron configurations of Kr, Xe, and Rn. The results are in excellent agreement with experiment or with other high level calculations where available. The current results for most of these species represent the best available values for the polarizabilities. The results show that the polarizability of H- is very difficult to calculate without extremely diffuse functions. The polarizability of H- is the largest value, 34.05 Å3, calculated for all species in the current study. The polarizabilities of the remaining halogen anions are also the best available values. The polarizabilities of the halogen anions (excluding F-) and H- have a linear correlation with the electron affinity of the neutral atom. Spin-orbit effects, even for closed shell species, cannot be ignored for quantitative accuracy, and the inclusion of spin-orbit effects for Fr+, Rn, and At- increases the polarizability by 4%, 6%, and 15%, respectively.

The 18-electron rule and electron counting in transition metal compounds: theory and application

The 18-electron rule and the corresponding methods for counting the total valence electrons of transition metal complexes are among the most useful basic tools in modern inorganic chemistry, particularly in its application to organometallic species. While in its simplest representation, the 18-electron rule is explained in that a closed, stable noble gas configuration of ns 2(n-1)d 10 np 6 is achieved with 18 valence electrons, this does not adequately explain the trends and exceptions seen in practice. As such, this report presents a deeper discussion of the 18-electron rule via molecular orbital models, stressing the roles of both σ- and π-bonding effects. This discussion thus aims to provide a better understanding of the relationship between electron count and stability, while also illustrating which factors can determine adherence (or not) to this commonly utilized rule. Lastly, the two common methods for electron counting (ionic and covalent models) are also presented with practical examples to provide the complete ability to apply the 18-electron rule.

Generation of high-energy mono-energetic heavy ion beams by radiation pressure acceleration of ultra-intense laser pulses

Generation of high-energy mono-energetic heavy ion beams by radiation pressure acceleration (RPA) of intense laser pulses is investigated. Different from previously studied RPA of protons or light ions, the dynamic ionization of high-Z atoms can stabilize the heavy ion acceleration. A self-organized, stable RPA scheme specifically for heavy ion beams is proposed, where the laser peak intensity is required to match with the large ionization energy gap when the successive ionization state passes the noble gas configurations [such as removing an electron from the helium-like charge state (Z−2)+ to (Z−1)+]. Two-dimensional particle-in-cell simulations show that a mono-energetic Al13+ beam with peak energy 1.0 GeV and energy spread of only 5% can be obtained at intensity of 7×1020 W/cm2 through the proposed scheme. A heavier, mono-energetic, ion beam (Fe26+) can attain a peak energy of 17 GeV by increasing the intensity to 1022 W/cm2.

Octacoordinate metal carbonyls of scandium and yttrium: theoretical calculations and experimental observation

The transition metal carbonyls are among the most important complexes in coordination chemistry. The maximum coordination number in these complexes is seven. Because the cations Sc(+) and Y(+) have empty second outermost d orbital subshells, they can possibly bond eight CO ligands, forming the 18-electron d(10)s(2)p(6) noble gas configuration. The aim of this study is to determine whether the octacoordinate metal carbonyls of Sc(+) and Y(+) exist. The structures and bonding of M(CO)n(+) (M = Sc and Y, n = 7-9) were studied using Density Functional Theory (DFT) calculations with the functionals of B3LYP and BP86. The cationic complexes from laser ablation of Sc and Y in CO gas were analyzed by time-of-flight mass spectrometry. The structures of M(CO)n(+) (M = Sc and Y, n = 7-9) and the bond dissociation energies for the last CO ligand in M(CO)n(+) (M = Sc and Y, n = 8 and 9) were obtained using DFT calculations. The products in the experiment for both metals include the series MO(CO)n(+), MO(H2O)(CO)n(+) and M(CO)n(+) (M = Sc or Y). The intensities of the MO(CO)n(+) and MO(H2O)(CO)n(+) ions change gradually with the number of CO ligands, while most M(CO)n(+) ions are very weak except for three intense ones, Sc(CO)7(+), Sc(CO)8(+) and Y(CO)8(+). Comparisons between the theoretical calculations and the experimental observations indicate that eight CO ligands are chemically bonded on the central atom in the singlet state of Sc(CO)8(+) ((1)A1 state of D(4d) symmetry) and the singlet and triplet states of Y(CO)8(+) ((1)A1 state of D(4d) symmetry and (3)A(1g) state of O(h) symmetry). The (1)A1 states of both Sc(CO)8(+) and Y(CO)8(+) have the 18-electron d(10)s(2)p(6) noble gas configuration. In M(CO)9(+) (M = Sc or Y), the ninth CO is weakly adsorbed on the external shell.

Periodicity in the formulae of carbonyls and the electronic basis of the Periodic Table

The basis of the Periodic Table is discussed. Electronic configuration recurs in only 21 out of the 32 groups. A better basis is derived by considering the highest classical valency (v) exhibited by an element and a new measure, the highest valency in carbonyl compounds (v*). This leads to a table based on the number of outer electrons possessed by an atom (N) and the number of electrons required for it to achieve an inert (noble) gas configuration (N*). Periodicity of these is nearly complete. The new basis helps to settle the question of the best form of table and related issues.

The electronic structures of vanadate salts: Cation substitution as a tool for band gap manipulation

The electronic structures of six ternary metal oxides containing isolated vanadate ions, Ba 3(VO 4) 2, Pb 3(VO 4) 2, YVO 4, BiVO 4, CeVO 4 and Ag 3VO 4 were studied using diffuse reflectance spectroscopy and electronic structure calculations. While the electronic structure near the Fermi level originates largely from the molecular orbitals of the vanadate ion, both experiment and theory show that the cation can strongly influence these electronic states. The observation that Ba 3(VO 4) 2 and YVO 4 have similar band gaps, both 3.8 eV, shows that cations with a noble gas configuration have little impact on the electronic structure. Band structure calculations support this hypothesis. In Pb 3(VO 4) 2 and BiVO 4 the band gap is reduced by 0.9–1.0 eV through interactions of (a) the filled cation 6 s orbitals with nonbonding O 2 p states at the top of the valence band, and (b) overlap of empty 6 p orbitals with antibonding V 3 d–O 2 p states at the bottom of the conduction band. In Ag 3VO 4 mixing between filled Ag 4 d and O 2 p states destabilizes states at the top of the valence band leading to a large decrease in the band gap ( E g=2.2 eV). In CeVO 4 excitations from partially filled 4 f orbitals into the conduction band lower the effective band gap to 1.8 eV. In the Ce 1− x Bi x VO 4 (0≤ x≤0.5) and Ce 1− x Y x VO 4 ( x=0.1, 0.2) solid solutions the band gap narrows slightly when Bi 3+ or Y 3+ are introduced. The nonlinear response of the band gap to changes in composition is a result of the localized nature of the Ce 4 f orbitals.

The Noble Gas Configuration - Not the Driving Force but the Rule of the Game in Chemistry

The physical origin of chemical bonding, ionic and covalent, is reviewed. It is re-emphasized that the striving for the noble gas configuration is not the driving force for chemical interactions, but rather is the outcome of various factors that govern the conduct of the chemical elements with one another.

Catalytic effects of metal oxides on the decomposition of Potassium perchlorate

Catalytic effects of metal oxides with comparable surface areas on the decomposition of potassium perchlorate were studied by thermogravimetric analysis. The catalytic mechanism is discussed based on the relative activity of the metal oxides. It is found that the oxides containing transition metal cations with partially filled d-orbitals have the highest activities, the oxides containing transition metal cations with completely empty valence d-orbitals are moderately active, and the oxides containing metal cations with completely filled d-orbitals or noble gas configurations have the lowest activities. Differences between the decomposition of potassium perchlorate and the previously reported decomposition of sodium chlorate are explained by differences in the melting points and molecular structures of these salts.

Catalytic decomposition of potassium chlorate

Thermal decomposition of potassium chlorate in the presence of various additives is studied using thermogravimetric analysis and differential thermal analysis. Catalytic effects of metal oxides with comparable surface areas are compared, and the catalytic effects of a number of nonoxide additives are also studied. The nonoxide additives show catalytic activities similar to the corresponding metal oxides. Metal cations and their electron configurations determine the catalytic activity of various compounds. Metal cations with partially filledd shells have the highest activity, transition metal cations with completely emptyd orbitals are moderated active, and metal cations with completely filledd shells or noble gas configurations have minimum activity.

Catalytic effects of nonoxide metal compounds on the thermal decomposition of sodium chlorate

Thermal decompositions of NaClO 3 in the presence of various non-oxide metal compounds were studied using thermogravimetric analysis. The non-oxide additives show catalytic activities similar to those of the corresponding metal oxides. The correlations between electron configurations and catalytic activities are discussed. It is found that metal cations with partially filled d orbitals are all active catalyst. Metal cations with d 0 configurations are moderately active. Metal cations with d 10 or noble gas configurations have the lowest activity

Catalytic effects of metal oxides on the thermal decomposition of sodium chlorate

The thermal decomposition of NaClO 3 in the presence of metal oxides was studied using thermogravimetric analysis. A number of metal oxides were prepared to have comparable surface areas, and their catalytic effects on NaClO 3 decomposition were compared. It was found that the catalytic activity depends on the electron configurations of the metal cations. Oxides containing metal cations with partially filled d-orbitals are all active catalysts for NaClO 3 decomposition. Transition metal cations with no d-electrons are moderately active. Metal oxides containing metal cations with completely filled d-orbitals or noble gas configurations have very little activity.

Synthese und Kristallstruktur von Mo(NO)(N3)3terpy, einem Nitrosyl-azido-Komplex des Molybdäns mit siebenfacher Koordination

Abstract Mo(NO)(N3)3terpy was obtained in form of yellow platelets from Mo(CO)3terpy and (CH3)3SiN3 in nitroethane as solvent. It crystallizes in the triclinic space group P1̄ with the lattice parameters a = 817.3, b = 866.7, c = 1416.2 pm, a = 71.97°, β = 102.15°, γ = 107.34°. The unit cell contains two monomeric complexes in which the central Mo atom exhibits the coordination number seven in a slightly distorted pentagonal bipyramid. One azido group and the nitrosyl ligand are in axial positions. NO+ coordinates in a linear arrangement (Mo-N-O = 176.2°) and acts as a three electron donor completing the noble gas configuration for the molybdenum atom. A weak trans effect of the NO-ligand causes different Mo-N distances to the axial (Mo-N31 = 218.4 pm) and the equatorial (Mo-N11 = 211.3, Mo-N21 = 212.9 pm) azido groups.

Ultrasonic absorption in the lanthanide sulphates

The rates of formation of the complexes MSO+4 have been measured using the ultrasonic pulse technique for the trivalent ions of yttrium, lanthanum, cerium, samarium, europium, gadolinium, dysprosium and ytterbium. Some justification for Eigen's three-step complex formation mechanism is reported. For metal ions with a noble gas configuration, the rates show a linear dependence on the inverse cation radius and, for transition metal ions, a similar dependence is observed after corrections for ligand field effects have been made. In the lanthanide sulphates series, ligand field effects are negligible. A more favourable comparison is possible with the alkaline earth metal ions, but only after allowance has been made for certain specific solvation effects in the lanthanide cations. The rates of formation are faster than for divalent cations of similar size. From the weight of evidence in favour of an increase in hydration number across the series, a kinetic model is proposed in which increased lability in the centre of the series is associated with a reaction path of lower activation energy relative to that for the lighter or the heavier elements.

Qualitative approach to the structural differences between some mixed metal oxides containing Sb 5+, Nb 5+ and Ta 5+

The structural differences between a number of mixed metal oxides containing Sb 5+, Nb 5+ and Ta 5+ ions are discussed in terms of the following three starting-points: 1. (a) the pentavalent metal ions will be as far from each other as possible due to Coulomb repulsion; 2. (b) an asymmetrical positive charge distribution around the anion favours polarization and covalency effects; 3. (c) a kind of metal ion-metal ion bond is possible between highly-charged metal ions with noble-gas configuration. Applications to several types of compounds are considered.