Chemistry for Changing Times 12 th Edition Hill and Kolb Chapter 3 Atomic Structure: Images of the Invisible John Singer Jackson Community College, Jackson, MI © 2010 Pearson Prentice Hall, Inc.

3/2 Electricity and the Atom Electrolyte: A compound that conducts electricity when molten or dissolved in water. Electrodes: Carbon rods of metallic strips that carry electrical current.

© 2010 Pearson Prentice Hall, Inc. 3/3 E Anode: A positive electrode. Cathode: A negative electrode. Electrolysis

© 2010 Pearson Prentice Hall, Inc. 3/4 Ions Ion: An atom or group of atoms with a charge. Anion: A negative ion. Cation: A positive ion.

© 2010 Pearson Prentice Hall, Inc. 3/5 Cathode Ray Tubes Mid-1800s: Crookes’ tube

© 2010 Pearson Prentice Hall, Inc. 3/6 Thomson Experiment 1897, Joseph John Thomson: Determined the charge:mass ratio of cathode rays (discovered electrons).

© 2010 Pearson Prentice Hall, Inc. 3/7 Goldstein’s Experiment: Positive Particles 1886, Goldstein: Observed positive rays using a perforated cathode.

© 2010 Pearson Prentice Hall, Inc. 3/8 Electron Charge 1909, Robert Millikan: Using the oil-drop experiment, Millikan discovered the charge of an electron.

© 2010 Pearson Prentice Hall, Inc. 3/9 X-Rays 1895, Wilhem Roentgen: Using a cathode ray tube, Roentgen discovered X-rays.

© 2010 Pearson Prentice Hall, Inc. 3/10 Radioactivity 1895, Antoine Becquerel: Discovered radioactivity. Marie Curie and husband Pierre characterized radioactivity.

© 2010 Pearson Prentice Hall, Inc. 3/11 Three Types of Radioactivity

© 2010 Pearson Prentice Hall, Inc. 3/12 Three Types of Radioactivity

© 2010 Pearson Prentice Hall, Inc. 3/13 Rutherford Gold Foil Experiment Using an apparatus similar to that shown below, Ernest Rutherford discovered the atomic nucleus.

© 2010 Pearson Prentice Hall, Inc. 3/14 Rutherford Gold Foil Experiment

© 2010 Pearson Prentice Hall, Inc. 3/15 Subatomic Particles

© 2010 Pearson Prentice Hall, Inc. 3/16 Atomic Structure Atomic number: The number of protons in a nucleus. Mass number: The sum of protons and neutrons in a nucleus.

© 2010 Pearson Prentice Hall, Inc. 3/17 Isotopes Isotopes have the same atomic number, but have different mass numbers (same number of protons, but different number of neutrons).

© 2010 Pearson Prentice Hall, Inc. 3/18 Nuclear Symbol Z X A X = Element symbol A = Atomic number Z = Mass number

© 2010 Pearson Prentice Hall, Inc. 3/19 Electron Arrangement: The Bohr Model Flame tests: Different elements give different colors to a flame.

© 2010 Pearson Prentice Hall, Inc. 3/20 Electron Arrangement: The Bohr Model Continuous spectra: When light emitted from a solid substance is passed through a prism, it produces a continuous spectrum of colors.

© 2010 Pearson Prentice Hall, Inc. 3/21 Electron Arrangement: The Bohr Model Line spectra: When light from a gaseous substance is passed through a prism, it produces a line spectrum.

© 2010 Pearson Prentice Hall, Inc. 3/22 Electron Arrangement: The Bohr Model Quantum: A tiny unit of energy produced or absorbed when an electron makes a transition from one energy level to another.

© 2010 Pearson Prentice Hall, Inc. 3/23 Electron Arrangement: The Bohr Model When electrons are in the lowest energy state, they are said to be in the ground state. When a flame or other source of energy is absorbed by the electrons, they are promoted to a higher energy state (excited state). When an electron in an excited state returns to a lower energy state, it emits a photon of energy, which may be observed as light.

© 2010 Pearson Prentice Hall, Inc. 3/24 Electron Arrangement Energy states or levels are sometimes called shells.

© 2010 Pearson Prentice Hall, Inc. 3/25 Electron Arrangement: The Quantum Model The Quantum model of the atom is a probability-based model. It is composed of principle energy levels, sublevels, and orbitals.

© 2010 Pearson Prentice Hall, Inc. 3/26 Electron Arrangement: The Quantum Model Principle energy levels (shells): Roughly correlate to the distance that an electron is from an atom’s nucleus. Sublevels (subshells): Each principle energy level (n) is divided into n sublevels. Orbitals: Orbitals are a region in space representing a high probability of locating an electron. Each sublevel has one or more orbital.

© 2010 Pearson Prentice Hall, Inc. 3/27 Electron Arrangement: The Quantum Model

© 2010 Pearson Prentice Hall, Inc. 3/28 Electron Arrangement: The Quantum Model

© 2010 Pearson Prentice Hall, Inc. 3/29 Electron Arrangement: The Quantum Model Electron configurations: Allow us to represent the arrangement of the electrons in an atom.

© 2010 Pearson Prentice Hall, Inc. 3/30 Electron Arrangement: The Quantum Model

© 2010 Pearson Prentice Hall, Inc. 3/31 Electron Arrangement: The Quantum Model The order-of-filling chart:

© 2010 Pearson Prentice Hall, Inc. 3/32 Electron Arrangement: The Quantum Model

© 2010 Pearson Prentice Hall, Inc. 3/33 Electron Configurations and the Periodic Table The periodic table is considered by many to be the most predictive tool in all of chemistry. It is composed of vertical columns called groups or families and horizontal rows called periods.

© 2010 Pearson Prentice Hall, Inc. 3/34 Electron Configurations and the Periodic Table Groups (families): Vertical columns in the periodic table. Groups contain elements with similar chemical properties. Periods: Horizontal rows in the periodic table. Elements in a period demonstrate a range of properties from metallic (on the left) to nonmetallic (on the right).

© 2010 Pearson Prentice Hall, Inc. 3/35 Electron Configurations and the Periodic Table Valence electrons: Valence electrons are the electrons in the outermost principle energy level of an atom. These are the electrons that are gained, lost, or shared in a chemical reaction. Elements in a group or family have the same number of valence electrons.

© 2010 Pearson Prentice Hall, Inc. 3/36 Electron Configurations and the Periodic Table Some groups in the periodic table have special names: Alkali Metals: Group 1A –Valence electron configuration: ns 1 Alkaline Earth Metals: Group 2A –Valence electron configuration: ns 2 Halogens: Group 7A –Valence electron configuration: ns 2 np 5 Noble Gases: Group 8A –Valence electron configuration: ns 2 np 6

© 2010 Pearson Prentice Hall, Inc. 3/37 Electron Configurations and the Periodic Table Metals, Nonmetals, and Metalloids: –Metals Metallic luster, conduct heat and electricity, malleable, and ductile. Examples are sodium and copper. –Nonmetals Dull luster, nonconductors, and brittle. Examples are sulfur and bromine. –Metalloids Demonstrate properties of both metals and nonmetals. Examples are silicon and arsenic.

© 2010 Pearson Prentice Hall, Inc. 3/38 Electron Configurations and the Periodic Table