element: Evolution of Modern Concepts
Evolution of Modern Concepts
Although much early work was done in chemistry, especially with metals, and many recipes were recorded, there were few developments in the conception of the elements. In the 16th cent. Paracelsus proposed salt, mercury, and sulfur as three “principles” of which bodies were made, although he apparently also believed in the four “elements.” Van Helmont (c.1600) rejected the four elements and three principles, substituting two elements, air and water.
Robert Boyle rejected these early theories and proposed a definition of chemical elements that led to the currently accepted definition. His definition is strikingly similar to Aristotle's earlier definition. In
Whereas Aristotle and other early philosophers tried to determine the identity of the elements solely by reason, Boyle and later scientists used the results of numerous experiments to identify the elements. In 1789 Antoine Lavoisier published a list of chemical elements based on Boyle's definition; this encouraged adoption of standard names for the elements. Although some of his elements are now known to be compounds, such as metallic oxides and salts, they were at the time accepted as elements since they could not be decomposed by any method then known.
In 1803 John Dalton proposed (as part of his atomic theory) that all atoms of an element have identical properties (including mass), that these atoms are unchanged by chemical action, and that atoms of different elements react with one another in simple proportions. Although symbols for some of the elements already existed, they were by no means universally accepted, and each compound also had a unique symbol that was unrelated to its chemical composition. Dalton devised a new set of circular symbols for the elements and used a combination of elemental symbols to represent a compound. For example, his symbol for oxygen was
Sections in this article:
- Discovery of the Elements
- Evolution of Modern Concepts
- Greek Concept of the Elements
- The Elements through the Ages
- Official Symbols and Names for the Elements
- Properties of the Elements
- Atomic Mass and Atomic Weight
- Atomic Number and Mass Number
- The Atom
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