This was later found to be too specific a model and was pushed aside for the current theory of quantum mechanics which is based on mathematics and describes a probability of “locating” an electron. Niels Bohr suggested that electrons move on orbits like planets around a sun.Ernest Rutherford later showed that most of the mass and all of the positive charge of an atom is found in a small dense core of the atom that we call the nucleus.JJ Thomson is credited with proving the first part of Dalton’s theory incorrect when he discovered the electron, as a result of his cathode ray tube experiment.His theory included the ideas that atoms make up all matter, are indivisible, and that atoms of an element are identical. John Dalton completed scientific experiments to develop his atomic model with evidence.He is also credited with using the word " atomos" to describe a small unit of matter that was unbreakable. Democritus is often credited with the first atomic theory, though it was a philosophical idea without evidence.He believed all substances were made of small amounts of these four elements of matter. He thought that all materials on Earth were not made of atoms, but of the four elements, Earth, Fire, Water, and Air. You can add more than one template to this assignment to give students lots of options! Suggested Scientists born on 384 BC died on 322 BC Aristotle did not believe in the atomic theory and he taught so otherwise. They can also describe the major advancements in each description box to make as detailed or general a timeline as is required by the level of chemistry they are studying.įor an alternative to the timeline layout, have students create a timeline poster to incorporate into a presentation or gallery walk. Students can upload pictures of these scientists or, in some cases, of their equipment, using Photos for Class. They should be sure to include a variety of different scientists and discoveries related to atomic theory in their timeline. Using a timeline layout, students will illustrate major atomic developments and outline how ideas changed over time. It is a valuable experience for students to understand that scientific ideas evolve over time in response to new and better data. Many lessons on atomic structure begin with a recitation of the historic developments that led to the current theory.
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