Elements early ideas about

The Greek philosophers thought that air, earth, fire, and water were the elements that formed all matter. Notice how the properties hot, dry, cold, and wet are associated with each element. These early ideas about the elements were not completely swept aside until the 19th century. 

Element The most fundamental form of matter at a chemical level. The great range of ideas about elements and what substances should be considered elements has driven chemical research for much of the history of civilization. Early thinkers generally assumed that there was a small number of elements (from 1 to 5), but today we recognize about 110 naturally occurring and artificial elements found on the Periodic Table of Elements. 

In spite of the high effort focused on the carbon electrochemistry, very little is known about the electrochemical preparation of carbon itself. This challenging idea appeared in the early 1970s in connection with the cathodic reduction of poly(tetrafluoroethylene) (PTFE) and some other perfluorin-ated polymers. The standard potential of the hypothetical reduction of PTFE to elemental carbon ... 

The idea of an element as a basic type of material, different from other materials, has been around for at least 2 million years, when the first people to make stone tools appeared on the scene. These early humans chose different types of rock for different tools, knowing that certain kinds of rock were more likely to break into small flakes or keep their sharp edge. Although they probably did not think about the building blocks of the rocks themselves, they knew that the material of some rocks was different from the material of other rocks. 

What Lavoisier had said about the unknowability of ultimate elements and the distinction between chemical species and physical atoms continued to trouble a lot of chemists long after the publication of Daltons ideas in the early 180os. Was it possible to reject Daltons chemical atomic theory while adopting everything else that he offered A significant minority of Daltons con-... 

Evolution of thinking about the importance of reactions between seawater and detrital clay minerals has come full circle in the past 35 years. Reverse weathering reactions were hypothesized in very early chemical equilibrium and mass balance (Mackenzie and Garrels, 1966) models of the oceans. Subsequent observations that marine clay minerals generally resemble those weathered from adjacent land and the discovery of hydrothermal circulation put these ideas on the back burner. Recent studies of silicate and aluminum diagenesis, however, have rekindled awareness of this process, and it is back in the minds of geochemists as a potentially important process for closing the marine mass balance of some element (see chapter 2). 

The mass of an atom is very small—much too small to be measured on a balance. Nevertheless, early chemists did find ways to isolate samples of elements that contained the same number of atoms. These samples were weighed and compared. The ratio of the masses of equal numbers of atoms of different elements is the same as the ratio of the masses of individual atoms. From this, a scale of relative atomic masses was developed. Chemists didn t know about isotopes at that time, so they applied the idea of what was then called atomic weight to all of the natural isotopes of an element. 

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