Alguns aspectos históricos da classificação periódica dos elementos químicos

A history of the periodic table of the elements is presented, from the first tentative classifications, passing through Meyer and Mendeleev, up to recent speculations on super-heavy elements still to be synthesized. Many of the discussions and discoveries related to chemical elements and their proper periodic classification are also presented.

Sobre os nomes dos elementos químicos, inclusive dos transférmios

The names of the chemical elements in Brazilian portuguese are presented, including a discussion of corresponding Brazilian nomenclature rules and translation of some parts of the pertinent IUPAC rules. The rules for naming groups of elements in the periodic table, as well as those for the symbolic indication of atomic number, mass number and electric charge of atoms, are also presented.

Referência geoquímica regional para a interpretação das concentrações de elementos químicos nos sedimentos da bacia do Lago Paranoá - DF

The present study aimed at determining a regional geochemical reference for sediment samples from Lago Paranoá watershed through the formulation of geoaccumulation indexes. The need for obtaining information from areas representing low human impact was the basis of this work. Systematic evaluations of sediment from Lago Paranoá will bring valuable information regarding the potential risk that this layer represents for aquatic organisms. Thus, despite the recent water quality improvements achieved in this ecosystem, contaminants incorporated in the sediments may be remobilized for alterations in the adjacent environment. The adsorption capacity of chemical elements in sediment samples was controlled through the variation in the amounts of organic matter, the mineralogical composition and the granulometric variation. By creating the Sediment Enrichment Index (SEI) through the normalization of analytical data it was possible to establish the magnitude of this enrichment relatively to naturally occurring concentrations all over the region of interest. Normalized values with organic matter were especially useful for the evaluation of lothic systems.

A tabela periódica dos elementos químicos prevista por redes neurais artificiais de Kohonen

Although several chemical elements were not known by end of the 18th century, Mendeleyev came up with an astonishing achievement: the periodic table of elements. He was not only able to predict the existence of (then) new elements but also to provide accurate estimates of their chemical and physical properties. This is certainly a relevant example of the human intelligence. Here, we intend to shed some light on the following question: Can an artificial intelligence system yield a classification of the elements that resembles, in some sense, the periodic table? To achieve our goal, we have fed a self-organized map (SOM) with information available at Mendeleyev's time. Our results show that similar elements tend to form individual clusters. Thus, SOM generates clusters of halogens, alkaline metals and transition metals that show a similarity with the periodic table of elements.

Caracterização dos níveis de elementos químicos em solo, submetido a diferentes sistemas de uso e manejo, utilizando espectrometria de fluorescência de raios-x por energia dispersiva (EDXRF)

This study aimed to evaluate the chemical elements levels in soil, submitted to different management systems and use by the Energy Dispersive X-Ray Fluorescence Spectrometry - EDXRF. The systems were T1 - agro forestry (SAF), T2 - Native Field (CN), T3 - Native Forest (NM), T4 - Tillage Forest (PF); T5 - conventional tillage system (SPC) and T6 - System tillage (NT). Samples were collected at 0-10 and 10-20 cm, dried and ground for analysis in EDX-720. The soil showed no difference in the average concentrations of chemical elements analyzed in the profiles, but the systems presented different concentrations of metal elements, and T3 had the highest K, Ca and Zn at 0-10 cm and higher contents of K, Ca, Cu, Zn and Mn in the layer of 10-20 cm.

Núcleos exóticos e síntese dos elementos químicos

We have around ninety chemical elements available in nature, which were produced mainly by nuclear reactions inside stars. The fusion reactions are the main synthesis process which generates the light and intermediate masses elements. The synthesis begins with the hydrogen burning reaching the region of iron mass nuclei. Heavier elements are synthesized by neutron capture processes, forming exotic nuclei with large neutron excess. These systems present characteristics very different from nuclei inside of stable atoms; they only occur in particular astrophysical environments or are produced artificially in special laboratory conditions. This work discusses some properties of the exotic nuclei and how they participate in the synthesis of elements.

Análise exploratória rápida e não destrutiva (screening) da presença de elementos químicos tóxicos em material escolar por fluorescência de raios x

Compulsory in Brazil, toy certification aims to prevent possible risks in toy use. The Brazilian National Institute of Metrology (INMETRO) establishes the maximum concentration of toxic elements (TE) that may be present in toys. This study evaluates the presence of TE in different crayons, gouache and modeling clays using X-ray fluorescence. This technique is fast, has low operating cost and minimum sample pretreatment, resulting in a clean procedure without reagent consumption and waste generation. Bromine (in gouache) and Barium (in crayons) were the only potentially TE identified in the samples studied.

Cubisistema de los elementos químicos : aplicaciones didácticas.

Se describe la manera de construir un Cubisistema de elementos químicos o tabla periódica tridimensional. Esta herramienta educativa, realizada de forma inderdisciplinar entre diferentes departamentos, ha sido utilizada en los niveles educativos de tercer y cuarto curso de enseñanza secundaria obligatoria y bachillerato. Sus objetivos son, entre otros, apoyar la labor del profesor de Química, motivar a los alumnos hacia el aprendizaje de la Química y manejar el Cubisistema para conseguir un fácil aprendizaje a través del juego. La obra incluye una unidad didáctica para cada uno de los niveles a los que va dirigida.

Taula periòdica dels elements químics. 'Tabla periódica de los elementos químicos'.

Programa en entorno MS-DOS para segundo ciclo de Secundaria en enseñanzas sobre Química. A partir de una base de datos que contiene los 103 primeros elementos de la tabla periódica, sus datos, descubridor, explicación de su nombre y otros apuntes de interés, permite trabajar con algunas de las propiedades físicas y químicas de esos elementos, intentando así que el alumno adquiera una información más comprensiva y relacionada de las piezas básicas de la Química y, a través de ella, de todos los temas relacionados.

La clasificación periódica de los elementos químicos.

Resumen de la revista

Los elementos químicos y sus compuestos binarios.

Material no publicado

O nome e o símbolo dos elementos químicos. 'El nombre y el símbolo de los elementos químicos'.

Se pretende dar respuesta al origen y razón de los nombres de cada elemento químico, su historia, descubridor, símbolos químicos, etc. Describe los antecedentes de la notación química, el origen de los nombres de los elementos y un listado detallado de los elementos y símbolos agrupados por familias (alcalinos, térreos, halogenados, etc). Incluye la normativa sistemática de la IUPAQ para los elementos novísimos, principios generales, reglas de nomenclatura y códigos.

Norma práctica general para la deducción de la fórmula electrónica de los elementos químicos.

Se presenta la solución para eliminar la retención de datos memorísticos a través de un método rápido, sencillo y seguro. Se trata de una norma práctica para la deducción de la fórmula electrónica de cualquier elemento, a través del cual, el alumno se encuentra en condiciones de interpretar y reproducir el cuadro general de distribución electrónica.

Efeito da aplicação de água residuária de graxaria em elementos químicos do solo e na produção e composição mineral de duas espécies forrageiras

Pós-graduação em Agronomia (Ciência do Solo) - FCAV

Una década de investigación en la localización celular de elementos químicos en musgos

Área de Ecología, Departamento de Biología Celular y Ecología, Facultad de Biología, Universidad de Santiago de Compostela