Dalton-- His legacy
John Dalton (1766-1844) is considered to be the father of modern atomic theory. Dalton, an English chemist, physicist and meteorologist developed the first useful atomic theory of mater around 1803. Dalton's theory formed the foundation for the science of chemistry and his atomic theory led to many significant applications including the development of the best model of The Atom and the description of the different phases of matter.. Dalton's theory was an outgrowth of the earlier work of others. Ancient Greek philosophers ha stalked about atoms and matter but they didn't have any experiential data to support their ideas. Dalton was able to provide data based on observation and experimentation that led to his famous atomic theory. Dalton's model showed that atoms were tiny, indivisible, indestructible particles and that each one had a certain mass, size, and chemical behavior that was determined by what kind of element they were. Dalton turned the prevailing idea of his day into a scientific theory that could be tested by experiment. Dalton's atomic theory led to two fundamental laws of nature--the law of conservation of mass and the law of definite composition which eventually led to the periodic table of elements.
In 1808 Dalton published the details of his atomic theory. It can be summarized by the following five basic principals.
1) All matter is composed of small particles called atoms that can (and do) form elements. Dalton's idea of an element (matter) is what we believe today--elements are chemical substances that cannot be decomposed by further chemicals means.
2) Atoms cannot be subdued, created or destroyed. Different elements could have atoms of different sizes and mass. This has come to be known as the Law of Conservation of Mass. The later discovery of nuclear fusion and fission has altered this viewpoint.
3) Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties. (Dalton's theory provided a natural way to regulate chemical compounds and led to his construction of the first periodic table of elements.) This part of the theory explained the law of definite proportions which stated that every chemical compound has a definite composition of mass.
4) Atoms of different elements can combine to form chemical compounds in simple whole-number ratios. (Compounds are formed from atoms of the constituent elements.)
5) Atoms are combined, separated, or rearranged in chemicals reactions. (Chemical reactions occur when atoms are rearranged.)
Dalton's theory explained many principals of chemistry with simplicity. His theory's value lies in the research ideas it contained. As each part of Dalton's theory was tested, new ideas about atoms were developed through experimentation, and new models were proposed and tested. Initially Dalton's ideas were reputed and provoked little reaction among the scientific community. While it has since been proved that some of the details of his original theory were incorrect, the core concepts of his theory remain valid and are foundational to the modern physical science. In order to honor his work, scientists referred one atomic mass unit as "Dalton" for many years.
In 1808 Dalton published the details of his atomic theory. It can be summarized by the following five basic principals.
1) All matter is composed of small particles called atoms that can (and do) form elements. Dalton's idea of an element (matter) is what we believe today--elements are chemical substances that cannot be decomposed by further chemicals means.
2) Atoms cannot be subdued, created or destroyed. Different elements could have atoms of different sizes and mass. This has come to be known as the Law of Conservation of Mass. The later discovery of nuclear fusion and fission has altered this viewpoint.
3) Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties. (Dalton's theory provided a natural way to regulate chemical compounds and led to his construction of the first periodic table of elements.) This part of the theory explained the law of definite proportions which stated that every chemical compound has a definite composition of mass.
4) Atoms of different elements can combine to form chemical compounds in simple whole-number ratios. (Compounds are formed from atoms of the constituent elements.)
5) Atoms are combined, separated, or rearranged in chemicals reactions. (Chemical reactions occur when atoms are rearranged.)
Dalton's theory explained many principals of chemistry with simplicity. His theory's value lies in the research ideas it contained. As each part of Dalton's theory was tested, new ideas about atoms were developed through experimentation, and new models were proposed and tested. Initially Dalton's ideas were reputed and provoked little reaction among the scientific community. While it has since been proved that some of the details of his original theory were incorrect, the core concepts of his theory remain valid and are foundational to the modern physical science. In order to honor his work, scientists referred one atomic mass unit as "Dalton" for many years.