1. Ch10 Sec1 Atoms & Atomic Theory

2. atoms Smallest particles of matter All substances are made of atoms Atoms join with other atoms to make new substances

3. How small is an atom? http://learn.genetics.utah.edu/content/begin/cells/scale/ Diameter = 0.000000001 cm

4. Basic structure of all Atoms protons (p + ) are heavy, positively charged particles neutrons (n o ) are heavy particles with no charge (neutral) electrons (e - ) are extremely light, negatively charged particles electron cloud: region that occupies most of the volume of the atom nucleus: nucleus: small, dense region in the center of an atom which contains a majority of the mass

5. Atoms are neutral Equal numbers of protons (+) and electrons (–) e - =7 p + =7

6. The Elements: Each element has a different number of protons (atomic number) Ex: Fluorine 9FFluorine18.99 atomic number = number of protons symbol name average atomic mass (amu-mass of one atom) 92UUranium238.0

7. Rutherford’s Gold Foil Experiment

8. Discovery Most of the volume of an atom is empty space Nucleus contains heavy, positively charged particles (protons)

9. Thomson Cathode-Ray Tube Discovery: Atoms contain negatively charged particles (electrons)

10. Electrons Bohr discovered that electrons orbit the nucleus at different energy levels Electron cloud model –Region (orbital) where electrons are likely to be found

11. Looking at atoms today… TEAM 0.5 world’s strongest transmission electron microscope at Lawrence Berkeley National Laboratory gold atoms forming between gold crystals