CHEM 5013 Applied Chemical Principles Chapters Six and Seven Professor Bensley Alfred State College Chapter Objectives Describe and explain the relationship between the wave and particle theories of light and electrons. Explain the true model of the atom using atomic orbital nomenclature concepts. Learn how to write electron configurations for atoms and ions. Chapter Objectives Explain the relationship between electron configurations, valence electrons and the Periodic Table. Describe the various types of chemical bonding (ionic and covalent) using valance electron concepts and Lewis Structures. Electromagnetic Spectrum The Wave Nature of Light Light can be described by four variables. Wavelength, : Frequency, : Velocity, c: Amplitude, A: The Wave Nature of Light c = 1 meter = 1 x 10 -9 nm What is the wavelength of blue light with a frequency of 6.4 x 1014 /s? Check your answer – visible light is in the range of roughly 380 to 750 nm Quantum Effects and Photons What happens when you put metal in a flame? Atoms naturally vibrate with a defined frequency depending on the solid Absorption: Emission: Quantum Effects and Photons Photons: E = h = hc Atomic Spectra The blue-green line of the hydrogen atom spectrum has a wavelength of 486 nm. What is the energy in one photon of this light? Fundamental Concepts of the Atom Electrons are depicted as clouds of negative charge surrounding the nucleus. The density of the small dots is related to the probability of finding an electron at a particular location. Atomic Orbitals Location of an electron is described by 4 quantum numbers: 1. 2. 3. 4. Think of them as addresses or locations: Streets Houses Rooms Orbital Diagrams and Pauli Exclusion Orbital Diagrams: Electron spin represented by arrows (Spin Up, Spin Down) Examples: Hydrogen, Helium, Lithium, Beryllium, Boron Pauli Exclusion Principle No two electrons in an atom can have the same four quantum numbers. Pauli Exclusion Principle Which of the following electron configurations or orbital diagrams are allowed and which are not allowed by the Pauli Exclusion Principle? If it is not allowed, explain why. a) 1s22s12p3 b) 1s22s12p8 c) 1s22s22p63s23p63d8 d) 1s22s22p63s23p63d11 e) 1s 2s Periodicity of Elements Period # gives outermost shell containing electrons in ground state. Group number gives the number of valence electrons. Write the electron configuration for Tellerium. (Atomic number = 52) How many valence electrons in an atom of Tellerium in the ground state? Building Up Principle Chemical properties of an element are primarily related to ground state electron configuration. Example (1st 11 elements) Do you see a pattern? This can be explained by the building up principle (Aufbau Principle) This order of subshells corresponds to increasing energy levels of the subshells We fill orbitals starting with lowest energy(1s) and proceed to highest energy (building up) Questions? So what happens when you get to Carbon? Hund’s Rule: What is the electron configuration for the ground state of sulfur? Look at the Noble Gases (Ne, Ar, Kr, Xe) – they are chemically inert. Why? Shorthand electron configuration: Core vs. Valence Electrons Two types of electrons represented in shorthand electron configuration: 1. Core electrons: 2. Valence electrons: Write the shorthand electronic configuration for Sulfur. So, how many valence electrons are there in Sulfur? Chemical Bonding - Video REVIEW – What is an ion? Ionic Bonds: Example: NaCl Na = + Cl = __ valence electrons? __ valence electrons? What happens to the valence electrons? FORMS Ionic Bonds You can simplify the equation using Lewis Electron-Dot Symbols Use Lewis Dot Symbols to represent the transfer of electrons in forming Calcium Oxide, CaO, from atoms. • Ca •• • + • O • • • •• 2+ • • Ca + • O • •• 2- Lewis Symbol Examples Use Lewis symbols to represent the formation of Calcium Chloride. Write the electron configuration and Lewis symbol for Ca 2+ Write the electron configuration and Lewis symbol for S 2- Covalent Bonds Covalent Bonds: Consider H2: H • • H Or HCl: : Cl: : • • H Lewis Dot Formulas Definition: : : : : Bonding Pair H Cl Lone Pair Octet Rule – Covalent Compounds Atoms in covalent compounds obtain noble gas configurations by sharing electrons. Octet Rule: Exception: Multiple Bonds Double Bonds Definition: Example: Carbon dioxide CO2 Triple Bonds Definition: Example: Acetylene C2H2 Lewis Structure Examples Write the Lewis Structures for the following: 1. 2. 3. OF2 H2O Carbon monoxide