1 / 20

The Atomic Model Through Time

The Atomic Model Through Time. (see p. 54-55 in text). Aristotle (460 B.C. – 370 B.C.). emphasized that nature consisted of four elements: air, earth, fire, and water. he did not believe in discontinuous or separate atoms, but felt that matter was continuous.

rupert
Download Presentation

The Atomic Model Through Time

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Atomic Model Through Time (see p. 54-55 in text)

  2. Aristotle (460 B.C. – 370 B.C.) • emphasized that nature consisted of four elements: air, earth, fire, and water. • he did not believe in discontinuous or separate atoms, but felt that matter was continuous

  3. Democritus (460 B.C. – 370 B.C.) • greek philosopher • first to suggest the existence of “atoms” (Greek word “atomos” = indivisible) • atoms indivisible and indestructible • no experimental support http://www.stenudd.com/myth/Greek/images/democritus_1628_Brugghen.jpg

  4. John Dalton (1766-1844) • english chemist and schoolteacher • used scientific method to test Democritus’s ideas • Dalton’s atomic theory • elements composed of atoms • atoms of the same element are alike • different atoms can combine in ratios to form compounds • chemical reactions can occur when atoms are separated, joined, or rearranged (but atoms are not created nor destroyed)

  5. J.J. Thompson (1856-1940) • English physicist • discovered the electron • thought atom was negative charges stuck in a positive charged lump • referred to as the “plumb pudding model”

  6. We still use Thompson’s “cathode ray tube” in TV and other applications

  7. Robert A. Millikan (1868-1953) • American physicist that continued Thompson’s work on electrons • Found the quantity of charge carried by an electron (one unit of negative charge) • Calculated the mass of an electron (1/1840th the mass of a hydrogen atom)

  8. Ernest Rutherford (1871-1937) “Like howitzer shells bouncing off of tissue paper!” • New Zealand physicist and former student of Thompson • proposed that the atom is mostly empty space • positive charges and almost of the mass are in a small, centralized region called the nucleus

  9. Evidence for Rutherford’s Conclusions http://www.cartage.org.lb/en/themes/Sciences/Chemistry/Generalchemistry/Atomic/BasicStructure/ErnestRutherford/ruther.gif Rutherford Flash Animation

  10. Try it Yourself! In the following pictures, there is a target hidden by a cloud. To figure out the shape of the target, we shot some beams into the cloud and recorded where the beams came out. Can you figure out the shape of the target?

  11. The Answers Target #1 Target #2

  12. Niels Bohr (1855-1962) • former student of Rutherford • electrons found only in specific circular paths (orbits) around the nucleus • based on information about how the energy of an atom changes when it absorbs and emits light • called these fixed energies “energy levels”

  13. Erwin Schrodinger (1926) • Austrian physicist • quantum mechanical model • probability of electron locations around the nucleus • not an exact orbit • led to the electron cloud model

  14. Werner Heisenberg (1927) • German physicist • Heisenberg Uncertainty Principle – impossible to know the exact position and velocity of a particle (electron) at the same time • “the observer affects the observed” http://www.deutsches-museum-bonn.de/ausstellungen/heisenberg/bilder/heisenberg_2.jpg

More Related