![]() However, some particles were reflected or scattered, which goes directly against Thompson's theory, resulting in a new atomic theory - the Rutherford model. Most of the particles went straight through the foil, as predicted by the plum pudding model. In this experiment, Rutherford aimed a ray of radioactive alpha particles at a thin gold foil. This model was later tested by Ernest Rutherford, who performed the gold foil experiment. An analogous example would be a muffin with blueberries, for example, where the berries are the negatively charged particles and the muffin is the positively charged space. This final piece was given the name of atomos, which translates to “indivisible”, and later down the line was adapted into the “atom” we know today.īased on Democritus' ideas and Antoine Lavoisier's law of conservation of mass, at the beginning of the 19 th century a British chemist named John Dalton further developed the atomic theory. He hypothesized that repeatedly cutting an object in half will eventually lead to a fundamental, indivisible fragment of said object. The earliest records of humans speculating about the fundamental makeup of the world come from Ancient Greece, where the philosopher Democritus developed the basis for the atomic theory around 430 BCE. The nuclear shell model, describing the distribution of nucleons in shells with different energy levels. The Bohr model, describing the atom as a small nucleus surrounded by orbiting electrons.ĭiscovery of the neutral particle - neutron. The structure of the atom - small, positively charged nucleus in the middle surrounded by mostly empty space. Discovery of negatively charged particles - electrons.ĭiscovery of p olonium and r adium, which are strongly radioactive elements. Theory about indivisible fragments "atomos" making up all matter.Ītomic theory, stating that all matter is made up of indivisible atoms, which differ in size and mass depending on the chemical element.ĭiscovery of positively charged particles - protons. A more in-depth breakdown of some of the major discoveries can be found later in the article. The full timeline of discoveries made in connection to the atom is compiled in the table below. In this article, we'll look at the history of discovering atoms and understanding their structure. Ancient Greeks had thought of this same principle and prompted the discovery and study of atoms. Or so they thought, as beyond atoms there are electrons, fermions and bosons, with quarks remaining the smallest things as far as we know. ![]() Over time, scientists found ways to continue the process of splitting things in half, far beyond our visible eye, and at last reached the fundamental building blocks of matter. Just to put it in perspective, a sheet of paper is roughly a million atoms thick. However, even then, we'd be far from reaching the final split, as this definition of "small" refers to a macroscopic scale. There is a page containing 8 multiple choice questions and the project rubric.What would happen if we took a piece of paper and repeatedly cut it in half? Eventually, it would become impossible to continue with regular tools such as scissors, as the piece would simply be too small. Some students get creative by decorating with ways to remember the models: "chocolate chip cookie dough" around Thomson's information or "Legos" around Democritus'. ![]() I encourage them to make the poster colorful in order to separate the information that belongs together. The students read through the Information Book, cut out the "Everything You Need" pages and organize the images and information boxes into their own timeline. The Information Book is now also included as a digital Google document so you can share it with your students on Google Classroom and save paper! ![]() They end up being the perfect size to fit all of the information/pictures, and they look great hung up in my classroom and are not too big!Ĭopy one "Information Book" (it looks fine in Black and White - I copy it back-to-back, put the pages into four plastic sleeves, and bulldog clamp the pages for use each year) and one set of the Directions and "Everything You Need to Make an Atomic Theory Timeline" per group or pair of partners. I provide them with 11" by 17" white construction paper for the "posters". I like to show this Ted Ed video before we begin: This project covers: Democritus, Aristotle and "the Death of Chemistry", Dalton, Thomson, Rutherford, Bohr, and the Modern Cloud Theory. The Atomic Theory Timeline Project is everything you need to give your chemistry students a nice background on the history of the atom! Students use skills of synthesizing informational text, organizing pieces of information into groups and then into a chronological order, and displaying the information in a clear and creative way.
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