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Catalyst – October (4-5+2), 2009 Homework in folder! 1. 2. Can people think that theories are correct even when they are not? How does this happen? Do you think that the earth could be hollow? Why or why not? Today’s Agenda Catalyst Atomic Theory Part 2 P.N.E and Atomic Math Work Time Exit Question Today’s Objectives SWBAT describe the evolution of atomic theory from 1898 to 1932. SWBAT to locate and describe protons, neutrons, and electrons in the modern atom. SWBAT do atomic math! Numero Cinco! - R. A. Millikan Experiment: Millikan Oil Drop Experiment When: 1909 Where: U.S.A!!!! Millikan’s Oil Drop Experiment Millikan’s Calculations – Whoa! What were Millikan’s conclusions? I have most accurately measured the charge of an electron: -1.59 x 10-19 Coulombs What were Millikan’s conclusions? I have also most accurately measured the mass of an electron: 9.109 x 10-31kg Numero Seis! - Ernest Rutherford Experiment: Gold Foil Experiment When: 1910 Where: Montreal Gold Foil Experiment Explained Alpha helium particles were shot through a piece of gold foil Think aluminum foil but thinner and made out of gold! Alpha helium particles are 8000 times more massive (bigger) than electrons, so Rutherford thought they would knock electrons out of the way, but they did not! http://micro.magnet.fsu.edu/electromag/java/rutherford/ Rutherford Gold Foil Experiment in Action! Animation Remember! This is the current model of the atom (Thanks to Thomson) More History Ernie’s (Rutherford) Big Adventure Thin Sheet of Gold Atoms What were Rutherford’s conclusions? Pretend you are Rutherford As Rutherford, what conclusion would you make based on the data from the Gold Foil Experiment? Hint: Positive repels positive, negative repels negative = - + - - - What were Rutherford’s conclusions? •Discovered the nucleus, a concentrated mass with positive protons! •Nucleus is in the center of the atom •The atom is mostly empty space Relative Size of an Electron to the Atom What’s this empty space idea? The atom is mostly empty space! The nucleus is TINY compared to the size of the entire atom! James Chadwick Experiment: Beryllium Foil Experiment When: 1932 Where: Cambridge (England) What were Chadwick’s conclusions? Neutral radiation emitted; therefore, the nucleus contains another subatomic particle called the neutron (has a neutral charge) PROTON NUCLEUS - - + - + - ELECTRON - + + - - - NEUTRON Atom Worksheet Introduce yourself to Mista’ Atom! Subatomic Particles Key Point #1: The three main subatomic particles are… Protons Neutrons Electrons PROTONS (purple = positive) Location: nucleus -27 Mass: 1.6726 x 10 kg Charge: 1+ NEUTRONS (no color = no charge) Location: nucleus -27 Mass: 1.6749 x 10 kg Charge: neutral ELECTRONS (in the red = negative) Location: outside nucleus -31 kg Mass: 9.1094 x 10 Charge: 1 The mass of 1,839 ELECTRONS = the mass of 1 NEUTRON! Electrons virtually have NO MASS! Review of Subatomic Particles Subatomic Particle Protons Neutrons Electrons Location Mass NUCLEUS 1.6726 x 10-27 kg NUCLEUS 1.6749 x 10-27 kg OUTSIDE NUCLEUS 9.1094 x 10-31 kg Charge 1+ NEUTRAL 1- Atomic Math! Key Point #2: Atomic math helps us to find… Number of protons Number of neutrons Number of electrons This helps us distinguish atoms from each other! Atomic Math Bylaws 1. 2. 3. The atomic number of an atom is the same as the number of ___________________. PROTONS The number of electrons is equal to the number PROTONS of _______________(in a neutral atom). Atomic mass is equal to the number of PROTONS _________________ plus the number of NEUTRONS _________________. pREVIEW of the Periodic Table Atomic Number Element Symbol Atomic Mass Work Time Complete the Atomic Structure worksheet Check your Atomic Math! Exit Question 1. 2. What was Rutherford’s contribution to atomic theory? Ruthenium has an atomic number of 44. It has an atomic mass of 101. How many protons, neutrons, electrons does a neutral atom of Ruthenium have?