Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Review: physical properties chemical properties Sep 213:27 PM Theory and Law a theory is an idea that is proposed and that can change over a period of time for example Darwin's theory of evolution continues to change as more evidence is found (fossils, new species, etc) a law is a pattern or relationship that can be proven repeatedly for example the law of gravity is constant and is proven everytime something falls on the floor Sep 213:44 PM 1 Theory or Law? place each idea below in the theory or law category LAW THEORY Scientists can clone dinosaurs Aliens live on other planets Water freezes at 100 C Clouds form due to evaportation Space has no end Trees use carbon dioxide Dogs are smarter then cats Tin is malleable Sep 277:24 PM The Atom today we know that all matter is composed of atoms atoms are composed of protons, neutrons electrons the center of an atom is a nucleus and it contains the protons and neutrons electrons circle the nucleus in different orbits depending on the atom a neutral atom has the same number of electrons and protons proton number is the atoms atomic number (How do we know all this???) Sep 277:53 PM 2 Development of Atomic Theory the information we know about the atom is known as the atomic theory the atomic theory has not always remained the same since it is a theory it has changed and developed as new scientists have come on the scene Sep 277:51 PM (1) Early Greeks (Empedocles, Democritus, Aristotle) 2500 years ago Empedocles claimed matter was made up of four elements: earth, air, wind and fire Democritus said that any object cut into smaller pieces would eventually become so small that it could not be cut any more (called this smallest piece atomos) Aristotle agreed with Empedocles and this idea became accepted for the next 2000 years (yikes) Sep 277:58 PM 3 There are only 4 elements and that's the bottom line because Aristotle said so!! Sep 278:06 PM 2. John Dalton (1766 1844) his theory is often called the billard ball model because he saw the atom as being the same throughout and being indivisible Each atom is the same throughout but diffent from other atoms, like these billard balls. Sep 278:08 PM 4 Dalton created his atomic theory: (a) all matter is made up of small particles called atoms (b) atoms cannot be created, destroyed or divided into smaller particles (c) all atoms of the same element are identical but they are different then the atoms of another element (d) compounds are created when atoms of different elements are joined Sep 277:48 PM 3. J.J Thomson (1856 1940) his theory is often called the raisin bun model he saw the negative electrons scattered throughout the positive area of the atom like raisins are scattered through a bun Just like a raisin bun Sep 278:20 PM 5 4. Ernest Rutherford (1871 1937) his theory is called the planetary model he saw electrons circling the center of the atom like planets circle the sun proposed that the atom is mostly empty space with a very small and heavy nucleus Oct 110:03 AM Rutherford Model Electrons circle the nucleus Oct 110:07 AM 6 5. Niels Bohr (1885 1962) built on the Rutherford model he believed that the electrons did circle the nucleus but did so at different energy levels (shells) each energy level could only contain a certain number of electons the Bohr model he created is the accepted model for the atom today Oct 110:09 AM Bohr Model My model is the best Oct 110:14 AM 7 Readings Pages 24 29 Questions: Page 29, #'s 2,3,4,5,6,7, Oct 110:15 AM 8