Atomic Theory: Difference between revisions
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==History== | ==History== | ||
===John Dalton: Law of Multiple Proportions and Atomic Mass=== | ===John Dalton: The Law of Multiple Proportions and Atomic Mass=== | ||
[[File:Daltons_symbols.gif|thumb| | [[File:Daltons_symbols.gif|thumb|Dalton's concept of atoms and molecules]] | ||
Working from the conservation of mass principle, chemist John Dalton determined the law of multiple proportions to understand how different elements combined in compounds. In 1803, he proposed that each element of the periodic table was composed of identical components, atoms, that were unique to each element. He also suggested that these atoms were not created nor destroyed when one element was combined with another. Dalton's empirical, experimentally-based work marked the first scientific theory of the atom. | Working from the conservation of mass principle, chemist John Dalton determined the law of multiple proportions to understand how different elements combined in compounds. In 1803, he proposed that each element of the periodic table was composed of identical components, atoms, that were unique to each element. He also suggested that these atoms were not created nor destroyed when one element was combined with another. Dalton's empirical, experimentally-based work marked the first scientific theory of the atom. | ||
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===Amedeo Avogadro: Avogadro's Law=== | ===Amedeo Avogadro: Avogadro's Law=== | ||
In 1811, [[Amedeo Avogadro]] studied gases and determined that the amount of volume a gas occupies is not determined by the mass of the gas. This allowed Avogadro to take more accurate atomic measurements of gases than Dalton, and differentiate atoms from molecules. | |||
===Robert Brown: Brownian Motion=== | ===Robert Brown: Brownian Motion=== | ||
A Scottish botanist, Robert Brown, studied the motion of tiny pollen particles in water in 1827. The particles followed complex paths, dubbed Brownian Motion. As early as 1905, Albert Einstein used Brownian Motion to predict the size of atoms and molecules. | |||
===J.J. Thomson: The Plum-Pudding Model=== | |||
[[File:Plum_pudding_model.svg|thumb|Tomson's Plum-Pudding Model]] | |||
Through his work with cathode rays, [[J.J. Thomson]] discovered the electron, and was the first to learn that atoms weren't actually "uncuttable" as initially thought. Thomson knew that atoms had a net neutral charge, but he only knew that negative particles existed. Thus, Thomson developed the "plum-pudding" model of negatively charged electrons floating in a sea of positive charge. (He likened the relationship of electrons to the sea of positive charge to that of plums in plum pudding.) | |||
==Examples== | ==Examples== | ||
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==Connectedness== | ==Connectedness== | ||
While classical physics applies to large objects moving much slower than the speed of light, modern physics deals with special cases of tiny objects, like atoms, subject to relativistic effects. Atomic theory is vital to understanding many quantum physics concepts that are covered in both Physics 2211 and 2212. | |||
== See also == | == See also == | ||
Revision as of 16:16, 1 December 2015
Claimed by: Caitlyn Caggia (ccaggia3)
Atomic theory states that matter is composed of discrete units, called atoms. The word "atom" comes from the Greek word for uncuttable, atomos. Scientists later discovered that atoms were indeed able to be broken into subatomic, or elementary, particles including protons, neutrons, and electrons. Atomic theory has evolved greatly over time, but the most recent model stems from quantum mechanics.
History
John Dalton: The Law of Multiple Proportions and Atomic Mass
Working from the conservation of mass principle, chemist John Dalton determined the law of multiple proportions to understand how different elements combined in compounds. In 1803, he proposed that each element of the periodic table was composed of identical components, atoms, that were unique to each element. He also suggested that these atoms were not created nor destroyed when one element was combined with another. Dalton's empirical, experimentally-based work marked the first scientific theory of the atom.
Dalton proposed a list of atomic weights in 1805. However, Dalton failed to recognize natural tendencies of elements in nature (for example, oxygen typically exists as a diatomic molecule as O_2). Dalton was unable to distinguish between atoms and molecules (groups of atoms).
Amedeo Avogadro: Avogadro's Law
In 1811, Amedeo Avogadro studied gases and determined that the amount of volume a gas occupies is not determined by the mass of the gas. This allowed Avogadro to take more accurate atomic measurements of gases than Dalton, and differentiate atoms from molecules.
Robert Brown: Brownian Motion
A Scottish botanist, Robert Brown, studied the motion of tiny pollen particles in water in 1827. The particles followed complex paths, dubbed Brownian Motion. As early as 1905, Albert Einstein used Brownian Motion to predict the size of atoms and molecules.
J.J. Thomson: The Plum-Pudding Model
Through his work with cathode rays, J.J. Thomson discovered the electron, and was the first to learn that atoms weren't actually "uncuttable" as initially thought. Thomson knew that atoms had a net neutral charge, but he only knew that negative particles existed. Thus, Thomson developed the "plum-pudding" model of negatively charged electrons floating in a sea of positive charge. (He likened the relationship of electrons to the sea of positive charge to that of plums in plum pudding.)
Examples
Be sure to show all steps in your solution and include diagrams whenever possible
Simple
Middling
Difficult
Connectedness
While classical physics applies to large objects moving much slower than the speed of light, modern physics deals with special cases of tiny objects, like atoms, subject to relativistic effects. Atomic theory is vital to understanding many quantum physics concepts that are covered in both Physics 2211 and 2212.
See also
Are there related topics or categories in this wiki resource for the curious reader to explore? How does this topic fit into that context?
Further reading
Books, Articles or other print media on this topic
External links
Internet resources on this topic
References
Chapter 30 of OpenStax Textbook
Physics Portal page on Atomic Theory