CHM 1020 Chapter 4
CHM 1020 Chapter 4 CHM 1020
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This 11 page Class Notes was uploaded by Rachel Belson on Friday February 12, 2016. The Class Notes belongs to CHM 1020 at Wayne State University taught by Maryfrances Barber in Fall 2015. Since its upload, it has received 22 views. For similar materials see Survey of General Chemistry in Chemistry at Wayne State University.
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Date Created: 02/12/16
Chapter 4 Thursday, February 4, 2016 4:48 PM Chemical bond: attractive force that holds atoms together An ion forms when an atom's number of electrons changes. Metals lose valence electrons Nonmetals gain valence electrons Zinc and cadmium is +2, silver is +1 ALUMINUM AND GALLIUM….ZINC, AND CADMIUM. ANNNDDDDDDSILVER. Group VIIA nonmetals gain 1 e: -1 F- is fluoride ion Cl- is chloride ion Br- is bromide ion Group VIA nonmetals gain 2 e: -2 O(-2) is oxide ion S(-2) is sulfide ion Se(-2) selenide ion Group VA (-3) N(-3) nitride ion P(-3) phosphide ion As(-3) arsenide ion Formula unit: smallest unit Ionic compounds are neutral Total positive charge = total negative charge NaCl Sodium and oxygen Na(+) and O(-2) so the formula unit is Na2O Metals take a positive charge. Exam 2 Page 1 Exam 2 Page 2 Exam 2 Page 3 Exam 2 Page 4 Exam 2 Page 5 Exam 2 Page 6 Exam 2 Page 7 Exam 2 Page 8 Exam 2 Page 9 Chapter 4 Book notes: 4.1 Chemical Bonds Chemical Bonds: an attractive force that holds two atoms together in a more complex unit A. Ionic Bond: a chemical bond formed through the transfer of one or more electrons from one atom or group of atoms to another atom or group of atoms B. Ionic Compound: any compound with an ionic bond C. Covalent Bonds: chemical bond formed through the sharing of one or more pairs of electrons between two atoms D. Molecular Compound: a compound in which a covalent bond is formed 4.2 Valence Electrons and Lewis Symbols Valence electron: an electron in the outermost electron shell of a representative element or noble gas element. Lewis Symbol: the chemical symbol of an element surrounded by dots equal in number to the number of valence electrons that are present of the element. *When drawing the symbols, the element must have one dot on each side before adding a second to a side. Generalizations: 1. Representative elements in the same group of the periodic table have the same number of valence electrons. 2. The number of valence electrons for representative elements is the same as the roman numeral periodic-table group numbers. 3. The maximum number of valence electronsfor any element is 8. 4.3 The Octet Rule The most stable configuration of electrons is in the noble gases because they have 8 electrons. Octet Rule: in forming compounds, atoms of elements lose, gain, or share electrons in such a way as to produce a noble-gas electron configuration for each of the atoms involved. 4.4 The Ionic Bond Model Ion: an atom or group of atoms that is electrically charged as a result of the loss or gain of electrons. Gains an electron, negative charge Loses an electron, positive charge 4.5 The Sign and Magnitude of Ionic Charge Generalizations: 1. Metal atoms containing 1, 2, or 3 valence electrons tend to lose electrons to acquire a noble gas configuration. a. Group IA: 1+ b. Group IIA: 2+ c. Group IIIA: 3+ 2. Nonmetal atoms containing five, six, or seven valence electrons tend to gain electrons to acquire a noble gas configuration a. Group VIIA: 1- b. Group VIA: 2- c. Group VA: 3- Isoelectronic Species: an atom and an ion, or two ions, that have the same number and configuration of electrons. Elements isoelectronic to Ne (because they have a 1s2, 2s2, 2p6 configuration) Exam 2 Page 10 Elements isoelectronic to Ne (because they have a 1s2, 2s2, 2p6 configuration) N3-, O2-, F-, Na+, Mg2+ Al3+ 4.6 Lewis Structures for Ionic Compounds Lewis Structure: a combinationof Lewis symbols that represent either the transfer or the sharing of electrons in chemical bonds. Symbols=elements, Structure=compounds 4.7 Chemical Formulas for Ionic Compounds Three Rules to Writing Chemical Formulas for Ionic Compounds 1. The symbol for the positive ion is always written first 2. The charges on the ions that are present are not shown in the formula. Ionic charges must be known to determine the formula; however the charges are not explicitly shown in the formula. 3. The numbers in the formula (subscripts) give the combining ratio for the ions. 4.8 The Structure of Ionic Compounds Formula unit: the smallest whole-number repeating ratio of ions present in an ionic compound that results in charge neutrality 4.9 Recognizing and Naming Binary Ionic Compounds Binary compound: a compound in which only two elements are present Binary Ionic Compound: an ionic compound in which one element is a metal and the other element present is a nonmetal. 4.10 Polyatomic Ions Polyatomic ion: an ion formed from a group of atoms (held together by a covalent bond) through loss or gain of electrons. 4.11 Chemical Formulas and Names for Ionic Compounds Containing Polyatomic Ions 1. When more than one polyatomicion of a given kind is required in a chemical formula, the polyatomic ion is enclosed in parentheses, and a subscript, placed outside the parentheses, is used to indicate the number of polyatomic ions needed. 2. So that the identity of polyatomic ions is preserved, the same elemental symbol may be used more than once in a chemical formula. 2/11/16:Started chapter 5 working with Lewis dot structures and shared electron pairs. Will post chapter 5 in next note set. Exam 2 Page 11