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27 Sept 2016 Agenda • Slip quiz • Notes- Atoms - back to • Isotopes Notes (POGIL) • Homework Slip Quiz - Based on the research you did for homework 1. Name two scientists whose work had some impact on the development of the Nuclear Model of the atom. 2. When scientists use a phrase such as “The Nuclear Model of the atom” what do they mean by the use of the word “model” in this context? Slip Quiz - Based on the research you did for homework 1. Name two scientists whose work had some impact on the development of the Nuclear Model of the atom. Stoney - naming electrons Roentgen - discovery X-rays Curies -discovery of radioactivity J. J. Thomson - discovery electrons Rutherford, Geiger, Marsden - discovery nucleus (protons) Chadwick - discovery of neutrons Model 2. When scientists use a phrase such as “The Nuclear Model of the atom” what do they mean by the use of the word “model” in this context? Model - a conceptual, physical or mathematical representation of a real phenomenon that is difficult to observe directly. Used to explain observations that have been made and predict possible future observations. https://www.learner.org/courses/essential/physic alsci/session2/closer1.html Atoms 1 nanometer (1 billionth of a meter) -9 1 nm = 10 m Fig. 1 STM topographic image of a single Co atom on Cu(111) shown in a light shaded view. Current 1 nA, sample bias -10 mV, T = 2.3 K. http://www.nist.gov/cnst/epg/atom_manipulation_stm.cfm Powers of 10 http://www.youtube.com/watch?v=0fKBhvDjuy0 The Structure of the Atom The Nuclear Atom Model System (part of the universe under consideration and study) https://www.youtube.com/watch?v=-FWxd78sOZ8 In Search of Giants Part 1 - The Building Blocks of Matter • Atoms consist of a “cloud” of fast moving negatively charged electrons surrounding a tiny, extremely dense (or massive, in sense that it contains most of the mass of the particle) nucleus containing positively charged protons and neutral neutrons • The nucleus contains virtually all of the atom’s mass, but occupies only about one ten-thousandth the volume of the atom • The electrons are held within the atom by their attraction to the positively charged nucleus The Structure of the Atom: Modern View cont. The Strong Nuclear Force protons are held together in the nucleus by the strong nuclear force that acts over short range (short distances) inside the nucleus only and can overcome the electrostatic repulsion between the positive protons (Note: There is accepted data from experiments to support each of these statements.)https://www.youtube.com/watch?v=kBgIMRV895w The Structure of the Atom: Modern View cont. Sub-subatomic particles quarks (up, down, charm, strange, top, bottom) beyond scope of this course; for the scale we need to understand chemical reactions, nuclear atom model is sufficient Experimental Support for Sub-atomic particles: J. J. Thomsen and Discovery of the Electron Cambridge Physics Rutherford Gold Foil Experiment - Live Demonstration (Backstage Science, Prof. Kennedy) showing existence of nucleus Properties of Subatomic Particles ( 4-1 p 97, 4-2 p 102) Electron Symbol Location Relative electrical charge Relative mass (amu) Actual mass (g) e Proton - in cloud surrounding the nucleus 1- Neutron + n0 In the Nucleus of the atom In the Nucleus of the atom p 1+ 0 1 1.007 276 1.008 665 1840 0.000 549 9.11 x 10 –28 1.673 x 10 – 24 1.675 x 10 – 24 Isotopes - Pogil Are all atoms of an element alike? Why? The following activity will help you learn the important structural characteristics of an atom. How do we classify atoms? How does the combination of subatomic particles affect the mass and charge of an atom? What are isotopes? This is just a sampling of what we will address. Throughout this activity you will want to keep both Model 1 and a periodic table handy. Model 1 Isotopes of Hydrogen protons 1 1 1 neutrons 0 1 2 Model 1 Isotopes of Carbon protons 6 6 6 neutrons 6 7 8 Model 1 Isotopes of Magnesium protons 12 12 12 neutrons 12 13 14 1. Refer to Model 1. What subatomic particles do the following symbols represent in the Atomic Diagrams? electron proton neutron Continue to check your responses. 3. Find the three elements shown in Model 1 on your periodic table. a. What whole number shown in Model 1 for each element is also found on the periodic table for that element? (edit the connecting line or write answer below the word) Hydrogen:- 1 Carbon:- 6 Magnesium:- 12 We are writing the number of protons for each particular element. 3b. The whole number in each box of the periodic table is the atomic number of the element. What does the atomic number of an element represent? The atomic number of an element represents the number of protons in the nucleus of an atom of that element. 3c. Where is the atomic number located in the isotope symbol ? The lower left corner of the isotope symbol is where the atomic number is written. 4. How many protons are in all chlorine (Cl) atoms? 17 protons ; atomic number = 17 b) “I think that some chlorine atoms have 16 protons.” This is not correct because if an atom has 16 protons, it has atomic number 16 and it would be called a sulfur atom. The student has misunderstood the relationship between the number of protons, the atomic number and the name of an element. VIP Question 5. a) How is the mass number determined? Mass number is determined by adding the number of protons and number of neutrons together. b) Why is this number called a “mass” number? In an atom the particles that carry the majority of the mass of the atom are the protons and the neutrons. When you have counted them all up you will have the approximate mass of that atom in atomic mass units (amu). 6. Atom I Atom II Number of protons 5 9 Number of neutrons 6 7 Mass number 11 16 7. a) The mass number is in the upper left corner of the isotope symbol. b) The mass number is shown as a numeral following the name of the atom, separated by a hyphen. Examples: carbon-12, hydrogen-3, magnesium-26 *Do not mix this up with what question 3 was asking for, where you were looking up the atomic number of the atom, the number of protons 8. Writing isotope symbols for the atoms in question 6. 11 16 B F 5 9 Atomic number 5, is Boron Protons plus neutrons was 11, so this is the mass number Atomic number 9, is fluorine, mass # 16 9. Boron-11 Fluorine-16 10. Fill in the following table. Isotope symbol 40 K 19 Atomic number 18 F 9 31 S 16 19 9 16 Mass number 40 18 31 Number of protons 19 9 16 Number of neutrons 40 - 19 = 21 18- 9 = 9 31- 16 = 15 11. a) All isotopes of a particular element have the same atomic number. For example, in Model 1 all the carbon isotopes have an atomic number of 6, all the hydrogen isotopes have an atomic number of 1 and all the magnesium isotopes have an atomic number of 12. b) All isotopes of an element do not have the same mass number. The fact that isotopes have different mass numbers is what makes them different isotopes of that particular element. For Example: Isotopes from Model 1 could be carbon-12, carbon-13, and carbon-14 (which shows us different mass number each time). VIP to have a definition that is as unambiguous as possible. 12. Isotope Definition: Isotopes are atoms of the same element so isotopes have the same atomic number and isotopes have the same number of protons as each other. However, isotopes have different numbers of neutrons (different mass numbers) from each other. Isotopes definition addendum 1 12. Please notice: Sometimes an isotope will have the same number of protons and neutrons -Example Carbon-12 (6 protons, 6 neutrons) But this does not have to be the case Example carbon-14 (6 protons, 8 neutrons) Isotopes definition addendum 2 12. Please notice: We humans do not invent elements and the number of protons and neutrons - we’ve counted what we find occurring in nature for each element. We have found that elements exist with patterns in the proportions of their isotopes. Homework Complete Isotopes POGIL - Including Extension Questions Notes from Textbook, Chapter 4, The Structure of the Atom, 4.1 Early Theories of Matter and 4.2 Subatomic Particles and the Nuclear Atom Heads up - Unit test - Classification of Matter and Atomic Structure - Wednesday October 5th.