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Atomic Theory

Atomic Theory. What Does Your Eye See?. Letter e magnified 40x. Letter e magnified 100x. Matter. Anything that has mass and volume. Matter is made of atoms. Atomic Theory. Have you ever watched a mystery movie and thought you knew who the criminal was?

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Atomic Theory

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  1. Atomic Theory

  2. What Does Your Eye See? Letter e magnified 40x Letter e magnified 100x

  3. Matter • Anything that has mass and volume

  4. Matter is made of atoms

  5. Atomic Theory Have you ever watched a mystery movie and thought you knew who the criminal was? Then changed your mind because of a new clue? The same thing really happens in science. Sometimes models must be changed as new information is gathered.

  6. Remember Models? -used for things that are *too small or too large to be observed *too difficult to be understood easily

  7. Models of Atoms • scientists use large models to explain something that is very small • used to explain data or facts that were gathered experimentally • these models are also theories

  8. Let’s look at how Atomic Models have changed over time First Stop: Greece In The Beginning

  9. In 440 BC proposed the atom (from the Greek atomos meaning “indivisible”) Described as hard particles made of a single substance that were always moving and formed different materials by joining together Democritus

  10. In 1803, after experimentation, Dalton published his atomic theory: All substances are made of atoms. Atoms are small particles that cannot be created, divided or destroyed. Atoms of the same element are exactly alike, and atoms of different elements are different. Atoms join with other atoms to make new substances. Dalton

  11. In 1897, J.J. Thomson identified an error in Dalton’s theory Discovered that there are small particles inside the atom Therefore, atoms can be divided into even smaller parts Negatively charged particles are called electrons Thomson

  12. Thomson • Plum pudding model • Thought that electrons were mixed throughout an atom, like plums in a pudding • Atom made of a positively charged material with the negatively charged electrons scattered through it

  13. Rutherford • Mostly empty space • Small, positive nucleus • Contained protons • Negative electrons scattered around the outside

  14. In 1911 Rutherford revised his theory Proposed that in the center of the atom is a tiny, extremely dense, positively charged part called the nucleus Rutherford

  15. Bohr • Electrons move in definite orbits around the nucleus

  16. Modern Model: Electron Cloud • There are regions inside the atom where electrons are likely to be found • Sometimes called the wave model • Spherical cloud of varying density • Varying density shows where an electron is more or less likely to be

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