HONORS CHEMISTRY - CHAPTER 4 ATOMIC STRUCTURE OBJECTIVES AND NOTES - V10 NAME: DATE: PAGE: THE BIG IDEA: ELECTRONS AND THE STRUCTURE OF ATOMS Essential Questions 1. What components make up an atom? 2. How are atoms of one element different from atoms of another element? Chapter Objectives 1. What was Democritus role in the development of the modern atomic theory? (4.1) 2. Describe Dalton s atomic theory. (4.1) 3. Differentiate between actual mass and relative mass. (4.2) 4. Differentiate between actual charge and relative charge. (4.2) 5. Discuss the structure of an atom including the location of the proton, electron, and neutron with respect to the nucleus. (4.2) 6. Distinguish between protons, electrons, and neutrons in terms of their relative masses, charges, and abbreviations. (4.2) 7. Explain the contributions of Antoine Henri Becquerel (Henri Becquerel) and Marie and Pierre Curie in the development of the modern atomic theory. (4.2) 8. Describe the work of J. J. Thomson. (4.2) 9. Describe the contributions of Robert Millikan. (4.2) 10. Describe Ernest Rutherford s gold foil experiment and its impact on the modern atomic theory. (4.2) 11. Compare and contrast atomic number and mass number, their importance, what they represent, and their abbreviations. (4.3) 12. Compare and contrast atoms, ions, and isotopes. (4.3) 13. Solve problems involving atomic number, mass number, and the number of protons, electrons, and neutrons in an atom or ion. (4.3) 14. Define an atomic mass unit. (4.3) 15. Demonstrate and be able to describe all aspects of laboratory safety rules and procedures. (Applicable every chapter) 1
4.1 Defining the Atom a. Early Models of the Atom 1. atom: The atom is so small. How small? It is so small that it is the smallest part of an element that maintains the properties of that element. It is an electrically neutral particle, therefore, it has no charge. 2. element: A substance that is composed of one kind of atom; it cannot be broken down by chemical means. All material in the universe is made up of elements, combinations of elements, or fragments of elements. Examples: carbon, aluminum, iron. 3. Democritus a. 400 BC. b. Atomos: Indivisible particles. 4. John Dalton a. Early 1800's. b. Discovered first modern atomic theory. 1. Each element is made up of tiny particles called atoms. 2. All atoms of the same element are identical, but they differ from those of any other element. 3. Atoms unite in definite ratios to form compounds. 4. Chemical reactions involve reorganization of the atoms; the atoms themselves are not changed. 5. Antoine Henri Becquerel (Henri Becquerel) a. Discovered radioactivity in the late 1800's. 6. Marie and Pierre Curie a. Late 1800's and early 1900's. b. Isolated radioactive elements. c. Along with the Henri Becquerel, P. Villard, and Ernest Rutherford (see below), they discovered the three basic types of radioactivity. 1. Alpha particles (α): Positive particles that are actually He - 4 nuclei. 2. Beta particles (β): High-speed negative particles. 3. Gamma Rays (γ): Very high-energy rays that have no charge. 2 - HC - Chapter 4 - Objectives and Notes - V10
4.2 Structure of the Nuclear Atom a. Subatomic Particles 1. J. J. Thomson b. Crooke's tube/cathode ray tube. c. Cathode rays are negatively charged particles: electrons (first person to really discover the electron). d. The speed of the electron. e. Charge/mass ratio for the electron. 1. e m = k a. e = amount of charge on the electron. b. m = mass of the electron. c. k= constant = - 1.76 x 10 8 coulombs/gram. 1. coulomb is a unit that measures electricity. 2. If you memorize the numerical value for k or any other constant you have no life. d. k was the same no matter what metal was used for the cathode. 1. all electrons are the same. f. Created the Plum Pudding/Rice Pudding/Raisin Bun/Chocolate Chip Cookie/Chocolate Sphere with Green M & M s theory of the atom. 2. Robert Millikan b. Oil drop apparatus. c. Experimentally found e = - 1.60 x 10-19 coulombs. d. Using the equation e = k he calculated the mass of the electron. m 1. Mass of the electron = 9.09 x 10-28 g. 3 - HC - Chapter 4 - Objectives and Notes - V10
a. The Atomic Nucleus 1. Ernest Rutherford b. Fired positively charged particles/alpha particles/helium nuclei at gold foil. c. Deflection of particles led to discarding the "dessert" theory of atomic structure. d. Created the nuclear or planetary model. 1. Center of atom is a sphere of positive charge (the nucleus-containing protons and neutrons). 2. Electrons orbit the nucleus in 3-D space. 3. Most of the atom is empty space. 4.3 Distinguishing Among Atoms a. Atomic Number and Mass Number 1. atomic number: The number of protons in the atom = number of electrons in the atom. Note: The identity of the element is determined by the number of protons in the atom. 2. mass number: The number of nucleons in the atom equals the sum of all of the particles found in the nucleus, which equals the sum of all of the protons and neutrons added together. 3. nucleon: Any particle found in the nucleus of an atom. Nucleons are either protons or neutrons. They are only distantly related to Klingons (See Star Trek - the original series). 4 - HC - Chapter 4 - Objectives and Notes - V10
b. Isotopes 1. isotopes: Atoms of the same element that have different numbers of neutrons. Thus, their mass numbers are also different. 2. valence electrons: Electrons on the outside energy level of an atom. 3. ion: 1. An atom or group of atoms that has lost or gained one or more electrons and thus carries an electrical charge. Examples: K +, F -, and PO 4 3-. a. cation: An ion with a positive charge. Examples: K +, Mg 2+, and NH 4 +. The names for monatomic cations do not change. Example: K + is the potassium ion. b. anion: An ion with a negative charge. Examples: F -, S 2-, and PO 4 3-. The name for monatomic anions end in -ide. Examples: F - is the fluoride ion and S 2- is the sulfide ion. c. Atomic Mass 1. atomic mass unit (amu): 1/12 the mass of one C-12 isotope. 2. atomic mass/atomic weight/average atomic mass/weighted average atomic mass: The weighted average mass of all of the isotopes of an element. Note: While mass number always refers to one atom, atomic mass refers to an average of masses. 5 - HC - Chapter 4 - Objectives and Notes - V10