Análise sobre diferentes abordagens de configuração eletrônica de elementos apresentados em livros de química

This study aimed to identify and review of the conceptual differences presented by authors of books, focusing on the theme of electronic configuration. It shows the changing concepts of electronic configuration, its implications for the cognitive development of students and their relations with the contemporary world. We identified possible obstacles in books generated in the search for simplifications, situations of different concepts of energy in the electron configuration for sublevels. For this analysis was carried out in several books, and some other general chemistry and inorganic chemistry without distinguishing between level of education, whether secondary or higher. It was found that some books for school books corroborated with higher education, others do not. To check the consistency of what was discussed, it was a survey of 30 teachers, it was found divergent points of responses, particularly with respect to the energy sublevels and authorship of the diagram which facilitated the electron configuration. It was found that the total 22professores, ie, 73,33% answered correctly on the energy sublevel more calcium (Ca) and 80%, ie, 24 teachers responded incorrectly on the iron. As for the authorship of the diagram used to facilitate the electronic configuration, we obtained 93, 33% of teachers indicated that they followed a diagram, and this was called "Diagram of Linus Pauling," teacher 01, 3,33%, indicated that the diagram was authored by Madelung and 01, 3,33%, did not respond to question. Was observed that it is necessary a more detailed assessment of ancient writings, as the search for simplifications and generalizations, not so plausible, lead to errors and consequences negative for understanding the properties of many substances. It was found that quantum mechanics combined with spectroscopic data should be part of a more thorough analysis, especially when it extends situations atoms monoelectronicpolieletrônicos to describe atoms, because factors such as effective nuclear charge and shielding factor must be taken into consideration, because interactions there is inside an atom, described by a set ofquantum numbers, sometimes not taken into account

Estudo teórico QTAIM e DFT dos compostos de coordenação: efeito quelato, titanocenos e ligação química

This work is a study of coordination compounds by quantum theory of atoms in molecules (QTAIM), based on the topological analysis of the electron density of molecular systems, both theoretically and experimentally obtained. The coordination chemistry topics which were studied are the chelate effect, bent titanocene and chemical bond in coordination complexes. The chelate effect was investigated according to topological and thermodynamic parameters. The exchange of monodentate ligands on polydentate ligands from same transition metal increases the stability of the complex both from entropy and enthalpy contributions. In some cases, the latter had a higher contribution to the stability of the complex in comparison with entropy. This enthalpic contribution is explained according to topological analysis of the M-ligand bonds where polidentate complex had higher values of electron density of bond critical point, Laplacian of electron density of bond critical point and delocalization index (number of shared electrons between two atoms). In the second chapter, was studied bent titanocenes with bulky cyclopentadienyl derivative π-ligand. The topological study showed the presence of secondary interactions between the atoms of π-ligands or between atoms of π-ligand and -ligand. It was found that, in the case of titanocenes with small difference in point group symmetry and with bulky ligands, there was an nearly linear relationship between stability and delocalization index involving the ring carbon atoms (Cp) and the titanium. However, the titanocene stability is not only related to the interaction between Ti and C atoms of Cp ring, but secondary interactions also play important role on the stability of voluminous titanocenes. The third chapter deals with the chemical bond in coordination compounds by means of QTAIM. The quantum theory of atoms in molecules so far classifies bonds and chemical interactions in two categories: closed shell interaction (ionic bond, hydrogen bond, van der Waals interaction, etc) and shared interaction (covalent bond). Based on topological parameters such as electron density, Laplacian of electron density, delocalization index, among others, was classified the chemical bond in coordination compounds as an intermediate between closed shell and shared interactions

Índice de aromaticidade baseado na deslocalização, degenerescência e densidade (D3BIA) para acenos e moléculas homoaromáticas

The aromaticity index is an important tool for the investigation of aromatic molecules. This work consists on new applications of the aromaticity index developed by teacher Caio Lima Firme, so-called D3BIA (density, delocalization, degeneracy-based index of aromaticity). It was investigated its correlation with other well-known aromaticity indexes, such as HOMA (harmonic oscillator model of aromaticity), NICS (nucleus independent chemical shielding), PDI (para-delocalization index), magnetic susceptibility (), and energetic factor in the study of aromaticity of acenes and homoaromatic species based on bisnoradamantanyl cage. The density functional theory (DFT) was used for optimization calculations and for obtaining energetic factors associated with aromaticity and indexes HOMA and NICS. From quantum theory of atoms in molecules (QTAIM) it was obtained the indexes D3BIA, PDI and . For acenes, when the over-mentioned indexes were applied it was observed no correlation except for D3BIA and HOMA (R2=0.752). For bisnoradamantenyl dication and its derivatives, it was obtained a good correlation between D3BIA and NICS. Moreover, it was evaluated solely one of the factors used on D3BIA calculation, the delocalization index uniformity (DIU), so as to investigate its possible influence on stability of chemical species. Then, the DIU was compared with the formation Gibbs free energy of some pairs of carbocations, isomers or not, which each pair had small difference in point group symmetry and no difference among other well-known stability factors. The obtained results indicate that DIU is a new stability factor related to carbocations, that is, the more uniform the electron density delocalization, the more stable the is carbocation. The results of this work validate D3BIA and show its importance on the concept of aromaticity, indicating that it can be understood from degeneracy of atoms belonging the aromatic site, the electronic density in the aromatic site and the degree of uniformity of electron delocalization

Efeito do campo elétrico em nanocones formados por aln e BN: um estudo por primeiros princípios

The development of computers and algorithms capable of making increasingly accurate and rapid calculations as well as the theoretic foundation provided by quantum mechanics has turned computer simulation into a valuable research tool. The importance of such a tool is due to its success in describing the physical and chemical properties of materials. One way of modifying the electronic properties of a given material is by applying an electric field. These effects are interesting in nanocones because their stability and geometric structure make them promising candidates for electron emission devices. In our study we calculated the first principles based on the density functional theory as implemented in the SIESTA code. We investigated aluminum nitride (AlN), boron nitride (BN) and carbon (C), subjected to external parallel electric field, perpendicular to their main axis. We discuss stability in terms of formation energy, using the chemical potential approach. We also analyze the electronic properties of these nanocones and show that in some cases the perpendicular electric field provokes a greater gap reduction when compared to the parallel field

Propriedades termo-eletrônicas da molécula do DNA

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Integrais de linha intervalares: fundamentos e aplicações

A necessidade de uma precisão e de uma aproximação dos resultados numéricos zeram com que diversas teorias surgissem: dentre elas, destacamos a Matemática Intervalar. A Matemática Intervalar surgiu na década de 60 com os trabalhos de pesquisa de Moore (MOORE, 1959) , em que ele propôs trabalhar com uma Matemática baseada na noção de intervalo real e não mais com um número como aproximação. Com isso, surgiu a necessidade de revisitar e reformular os conceitos e resultados da Matemática Clássica utilizando como base a noção de intervalo de Moore. Uma das áreas da Matem ática Clássica que tem tido muitas aplicações em engenharias e ciências é a Análises Numérica, onde um dos seus pilares é o Cálculo Integral e em particular as integrais de linha. Assim, é muito desejável se ter um cálculo integral dentro da própria Matemática Intervalar. No presente trabalho apresenta-se uma noção de Integral de Linha Intervalar baseada na extensão de integração proposta por Bedregal em (BEDREGAL; BEDREGAL, 2010). Para a fundamentação apresenta-se incialmente uma introdução sobre a pespectiva em que o trabalho foi realizado, considerando alguns aspectos histórico-evolutivos da Matemática Clássica. Os conceitos de Integrais de Linha Clássica, bem como algumas das suas aplicações mais importantes. Alguns conceitos de Matemática Intervalar necessários para o entendimento do trabalho. Para nalizar propomos uma aplicação da integral de linha em um experimênto clássico da mecânica quântica (a difração de um elétron em uma fenda) que graças ao fato de ser a Matemática Intervalar utilizada, nos dá um foco mais detalhado e mais próximo da realidade

Poço quadrado quântico finito e método de fatorização

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Solução analítica do potencial de Morse em mecânica clássica

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Teoria algébrica de processos da medida em sistemas quânticos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Gravitação semiclássica

Fazemos aqui uma breve descrição da teoria semiclássica da gravitação que tem conseguido antecipar de forma bastante robusta alguns efeitos de gravitação quântica.

Basicities of primary arylamines and calculated amine nitrogen electronic charges

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chlorophyll fluorescence of tropical tree species in a semi-deciduous forest gap

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

O papel dos modificadores de rede na produção da fotoluminescência no CaWO4

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Existe o quadrinho no vazio entre dois quadrinhos? (ou: o Koan nas histórias em quadrinhos autorais adultas)

Pós-graduação em Artes - IA

Soluções da equação de Fokker-Planck para um potencial isoespectral ao potencial de Morse

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)