Chemistry 1 West Linn High School Unit 2 Packet and Goals Name: Period: Unit 2 Atomic Structure and Nuclear Chemistry Unit Goals: As you work through this unit, you should be able to: 1. describe Dalton s atomic theory and compare to our modern understanding of the atom (4.1) 2. distinguish among protons, electrons, and neutrons in terms of mass and charge. (4.2) 3. describe the structure of the atom. (4.2) 4. explain why isotopes differ and why atomic masses are not whole numbers. (4.3) 5. understand how atomic mass is calculated. (4.3) 6. describe the three main types of nuclear radiation (25.1) 7. complete transmutation nuclear equations (25.2) 8. distinguish fission reactions from fusion reactions (25.3) Reading: Chapter 4: (pp 102-124) Sections 4.1 4.3 Chapter 25: (pp 874-893) Sections 25.1-25.3 Key Terms: atom, electrons, neutrons, nucleus, protons, atomic number, mass number, atomic mass, atomic mass unit, isotope, radioisotope, alpha, beta, gamma, transmutation, fission, fusion, Dalton s atomic theory, Plum Pudding Model, Rutherford s Gold Foil Experiment Homework: Classwork and Labs Description Goals HW 1 Atomic Structure 1-4 Unit 2 Note Packet Unit 2 Worksheet Packet Atoms and Isotopes Simulation HW 2 Isotopes 4-5 Indirect Measurement Activity Vegium Lab HW 3 Nuclear Chemistry 6-8 Nuclear Chem Simulations Activity Unit 2 Exam 1
4.1 Defining the Atom Early Models of the Atom: Page 102 Chapter 4 A. Define an Atom B. Democritus s Atomic Philosophy C. Dalton s Atomic Theory 1. All elements are composed of tiny indivisible particles called atoms. 2. Atoms of the same element are identical. Atoms of different elements are different. 3. Atoms combine in simple whole number ratios. 4. Atoms of one element are never changed to atoms of another element during chemical reactions. Sizing up the Atom: Page 103 A. What instruments can be used to observe individual atoms? 2
4.2 Structure of the Nuclear Atom Subatomic Particles: Page 105 A. What are the 3 kinds of subatomic particles? Electrons: J.J. Thomson 1897 Discovered the electron using a cathode ray tube (CRT) Negatively charged particles Protons: E. Goldstein 1886 Discovered the proton by careful observations of another ray in the Cathode Ray tube Positively charged particles Neutrons: James Chadwick 1932 Discovers the neutron Neutrons are the glue that holds the nucleus of the atom together. Atomic Charges 3
Plum Pudding Model Electrons evenly distributed in an atom filled with uniform positive chare First Atomic Model The Atomic Nucleus: Page 107 A. Summary of the Gold Foil experiment performed by Rutherford (page 108) B. The Rutherford Atomic Model (page 108-109) 1. An atom is mostly space. 2. There is a nucleus in the middle of the atom containing the protons 3. The electrons orbit a large distance away from the nucleus. 4. Proposes a Solar System or Orbital model of the atom Atomic Particle Summary Name Symbol Charge Mass (amu) Electron proton neutron 4.3 Distinguishing Among Atoms Atomic Number and Mass Number: Page 112 Define Atomic Number: 4
Define Mass Number: How to find the number of Neutrons in a Nucleus: Sample Problem 4.2 (page 114) How many protons, electrons, and neutrons are in each atom? 9 20 23 a. 4 Be b. 10 Ne c. 11 Na Example Problems (page 114) 18 19 Isotopes: Page 114 Define: Isotope Atomic mass unit: Unit of mass for atomic nuclei 1 amu = 1/12 the mass of Carbon- 12 Isotopic Symbols: Atomic Mass: Weighted average mass of all the naturally occurring isotopes in a sample of an element Atomic Mass: Page 116 5
Sample Problem 4.5 (page 119) Element X has two naturally occurring isotopes. The isotope with a mass of 10.012 amu has a relative abundance of 19.91%. The isotope with a mass of 11.009 amu has a relative abundance of 80.09%. Calculate the atomic mass of element X. Example Problems: Page 119 24 25 Regular Chemistry vs. Nuclear Chemistry Regular Chemistry Deals with the arrangement of atoms to form compounds Never about the changing of the nucleus Elements NEVER change to other Elements Chapter 25 Nuclear Chemistry Deals with the decay of unstable isotopes to form a stable nucleus About the changing of the nucleus Elements CAN change to other Elements 25.1 Nuclear Radiation Define: Radiation Property Alpha Beta Gamma Composition Alpha Particle (helium nucleus) Beta Particle (electron) High-Energy Radiation Symbol Radioactive Decay Charge Mass (amu) Penetrating Power Radioisotope 6
Alpha Radiation (page 877) Example Beta Radiation (page 878) Example Gamma Radiation (page 879) Examples 25.2 Nuclear Transformations What holds the nucleus together? Strong Nuclear Force Short range, attractive force that acts among nuclear particles Neutrons and Protons attract one another! Much stronger than electrical or gravitational force Electromagnetic Force Repulsive force between protons. Tries to pull the nucleus apart. Stable Nucleus Correct balance of Strong Nuclear & Electromagnetic Forces Correct p + to n ratio MOST ATOMS ARE STABLE!! Band of Stability 7
Most common transformation particles Radiation Name Symbol & Iso. Notation Charge Mass Alpha particle Beta particle Gamma radiation Positron Neutron Proton Nuclear Stabilization Equations Alpha emission: Uranium-238 Transformation Examples Silicon-27 + β Beta emission: Carbon-14 Bismuth-214 + α Positron emission: Oxygen-15 Aluminum-27 + α Silicon-30 + Neutron emission: Silver-107 25.3 Fission and Fusion Define Fission Large nucleus breaking down into smaller nuclei Define Fusion Smaller nuclei combining to larger nucleus 8