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Ionic and Metallic Bonding

Ionic and Metallic Bonding. Chapter 7. 7.1 Ions. An ion is an atom that has gained or lost electrons from the valence shell. Valence electrons are the electrons contained in the highest occupied energy level These electrons will mostly determine the chemical properties of the element

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Ionic and Metallic Bonding

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  1. Ionic and Metallic Bonding Chapter 7

  2. 7.1 Ions • An ion is an atom that has gained or lost electrons from the valence shell. • Valence electrons are the electrons contained in the highest occupied energy level • These electrons will mostly determine the chemical properties of the element • For representative elements, group # = # valence electrons • Exception is Helium with 2 valence e-

  3. Electron Dot Structures • Diagrams that show the number of valence electrons • Also called Lewis Dot Diagrams

  4. The Octet Rule Magic # = 8 • Gilbert Lewis recognized that Noble Gases are inert. • These elements have a full s and p sublevel and with the exception of Helium have 8 valence e-. • He realized that atoms will bond in order to achieve noble gas e- configuration. • Atoms of metals tend to lose their valence e-, leaving a complete octet in the next lowest energy level. Atoms of nonmetals tend to gain e- or to share e- with one another to complete an octet.

  5. Formation of Cations • An atom’s loss of valence e- produces a cation, or (+) charged ion. • Metals have relatively low ionization energy. It requires less energy to remove 1,2,3, or 4 valence electrons. • Metals have relatively low electronegativity and are not likely to gain electrons. • Metals will typically lose all valence electrons and have a charge equal to the number of electrons lost.

  6. E- Configuration of cations • Atoms will lose valence e- in order to achieve the electron configuration of the nearest noble gas. e- configuration for Ne

  7. Transition Metals • Transition metals do not always form Noble gas electron configuration when forming cations. • Because of the partially filled d sublevel, they form pseudo noble gas configurations • Silver will form a +1 ion • Copper can form +1 or +2

  8. Naming Cations • Once electrons are removed from a neutral atom a positive charge will exist. • For cations, the name of the metal is the same as the name of the cation. • Al is called aluminum. • Al+3 is still called aluminum.

  9. Formation of Anions • The gain of negatively charged electrons by a neutral atom produces an anion. • Most nonmetals have more than 4 e- in the valence shell. • They will gain e- in order to achieve the noble gas configuration of the nearest noble gas.

  10. Naming Anions • When atoms from group 7A gain e-, they will have a charge of -1. These anions are called halide ions. • Once a nonmetal gains electrons, the name of the ion will be different from the name of the neutral ion. • For monatomic anions, drop the ending and add –ide. • Ex: Oxide, Phosphide, Sulfide, Fluoride, Chloride

  11. 7.2 Ionic Bonds • Compounds composed of cations and anions are called ionic compounds. • Ionic compounds are typically neutral. • The electrostatic forces that hold ionic compounds together are called ionic bonds. • Just like when forming ions, ionic compounds consist of cations and anions seeking a complete octet.

  12. Formula Unit • A chemical formula shows the kinds and numbers of atomic in the smallest representative unit of a substance. • Ionic compounds are not typically found as just one unit. Typically a regular, repeating pattern of ionic bonds will exist. • In other words, a compound like NaCl will be connected to several other NaCl units. • A formula unit is the lowest whole-number ratio of ions in an ionic compound.

  13. Predicting Formula Units • Write the formula for both the cation and the anion. • Eliminate the (+) and (-) charges. • “Drop and drag” the numbers remaining as subscripts for the formula unit. • No charges will remain in the final formula.

  14. Practice Formula Writing and Naming

  15. Properties of Ionic Compounds • Most ionic compounds are crystalline solids at room temperature. • Arranged in regular, repeating, 3-D patterns • Structure is related to coordination number (number of oppositely charged ions surrounding an ion.) • See some examples here. • Ionic compounds have high melting points. • Ionic compounds conduct an electric current when melted or dissolved in water.

  16. 7.3 Bonding in Metals • Metals are made up of closely packed cations rather than neutral atoms. • The valence electrons of metals can be modeled as a sea of electrons. • Valence e- are mobile and can drift freely • Metals are ductile and malleable • Metals conduct electricity • Metal atoms are arranged in very compact and orderly patterns. • Check out this cool Nova Explanation of metals!

  17. Alloys • Alloys are mixtures composed of two or more elements, at least one of which is a metal. • Alloys are important because their properties are often superior to those of their component elements. • Sterling silver: silver and copper • Bronze: copper and tin • Steel: iron, carbon, boron, chromium, manganese, molybdenum, nickel, tungsten, and vanadium

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