Warm Up 9-8-17 Express 0.000 000 6988 in scientific notation Water has a ratio of 2 hydrogen atoms to 1 oxygen atom. What law explain this? Which part of Dalton’s atomic theory is no longer true? Pass out Periodic table Video DE - Chemistry Basics: Atomic Theory and the Periodic Table Lab Conservation of Mass? Check Conservation of Mass lab at the end of class with summary Agenda Mystery box observation Notes Unit 2-2 Turn in Archimedes’ Lab Homework Next Class – Bring pennies Sept 14 – Quiz unit 2

Unknown Structure Activity Purpose: Determine how the strings are attached on the interior of the box  Observations: Draw a picture of how the strings are attached inside the box Build it: Use strings, a styrofoam cup, scissors to build a model of the mystery box

Answer These Questions in Your Notebook What were the challenges? How did the model on your paper compared to the actual model that you created? How did you know what’s inside the box even though you can’t see it?

Unit 2-2 Structure of Atoms

Thompson’s Experiment J.J. Thompson a physicist that created the CRT (cathode-ray tube) To study current Experimented in 1887 CRT – airless glass tube, modifications lead to the the development of modern TV in 1928, Pointilism - Seurgat

Thompson’s Experiment CRT cathode electrode has negative charge anode has positive charge Deflected by a magnet = beam has a charge Magnet and TV demo Glowing beam come from the cathode end

Thompson’s Experiment The Electron The CRT beam moved a paddle wheel Electron consists of particles that have mass and a negative charge -Read only: e- are negatively charged but atoms have no charge, therefore atoms must contain + charge to balance the charges

Thompson’s Experiment “Plum Pudding” atomic model Discovered Think it exists

Rutherford’s Experiment Rutherford conducted gold-foil experiments and discovered the nucleus and confirm the existence of protons. Rutherford, a former student of Thompson disproved the plum pudding model in 1909

Gold-Foil Experiment 2 years later he came up with an explanation of what he observed

Rutherford’s Experiment Only a positively charged particle could repel the positively charged alpha beam The mass of this particle has to be larger than the incoming beam to deflect it Most of the atom is empty space that’s why only some beams were deflected

Subatomic Particles The nucleus is made up of protons and neutrons Proton: has a positive charge Electron: has negative charge Neutron: no charge. A neutral atom has no net charge, means # of protons = # of electrons. https://www.youtube.com/watch?v=aNK1mQfNeik - ATOMS BILL NYE The radius of the atom is more than 10,000 times bigger than the nucleus Nucleus is like a marble in the middle of a football stadium Proton’s mass is 2000 times heavier than electrons

Changes to Rutherford Model Neutron added to the nucleus Discovery of subatomic particles - smaller parts that make up an atom: Electrons (-), protons (+), and neutrons (0)

Assignments Summary: Compare Thompson’s experiment to Rutherford’s experiment. Which subatomic particle did each person discover? Finish & Turn in lab today Work on worksheet 2-2 taped, glued or stapled in the notebook Bring pennies next class (2-3 pennies)

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