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Ionic and Metallic Bonding
Chapter 7 Ionic and Metallic Bonding
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Section 1 Ions
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Learning Targets 7.1.1 – I can determine the number of valence electrons in an atom of a representative element – I can explain how the octet rule applies to atoms of metallic and nonmetallic elements – I can describe how cations form – I can explain how anions form.
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Valence Electrons Valence electrons – electrons in the highest occupied energy level of an elements atoms. Valence electrons determine an elements properties.
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To find the number of valence electrons simply look at the group number.
Helium is the only exception to this, only has 2 electrons. Electron dot structure – diagrams that show the valence electrons as dots.
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The Octet Rule Octet rule – in forming compounds, atoms tend to achieve the electron configuration of noble gases. Or the configuration of ns2np6
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Atoms of metallic elements tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level. Atoms of nonmetallic elements tend to gain electrons or share electrons with another nonmetallic element to achieve a complete octet.
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Formation Of Cations An atom’s loss of valence electrons produces a cation, or a positively charged ion. Usually metal atoms – very few nonmetals lose electrons.
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Transition metals will achieve the most stable configuration possible so they may be exceptions to the octet rule. Also called a pseudo-noble gas electron configuration.
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Which looks like
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Formation Of Anions The gain of negatively charged electrons by a neutral atom produces an anion. Nonmetals form anions and change their name endings to – ide. Halide ion – ions produced when atoms of chlorine and the other halogens gain electrons.
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Which looks like
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Section 2 Ionic Bonds and Ionic Compounds
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Learning Targets 7.2.1 – I can explain the electrical charge of an ionic compound – I can describe three properties of ionic compounds.
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Formation of Ionic Compounds
Ionic compound – compounds composed of cations and anions. Although they are composed of ions, ionic compounds are electrically neutral. Sodium reacting with chlorine 1 Sodium reacting with chlorine 2 Aluminum reacting with bromine Sodium reacting with bromine Aluminum reacting with iodine
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Ionic Bonds Ionic bonds – electrostatic forces that hold ions together in ionic compounds. Think about sodium and chloride Sodium has 1 valence electron. Chlorine has 7 valence electron. When they combine sodium gives chlorine its 1 valence electron so they both satisfy the octet rule.
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Formula Units Chemical formulas – shows the kinds and numbers of atoms in the smallest representative unit of a substance. Formula unit – lowest whole-number ratio of ions in an ionic compound.
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Examples: Look at sodium and oxygen
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Examples: Look at aluminum and oxygen
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Examples: Pick a metal from the representative elements.
Pick a nonmetal from the representative elements
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Properties OF Ionic Compounds
Most ionic compounds are crystalline solids at room temperature. Ionic compounds generally have high melting points.
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Coordination number – number of ions of opposite charge that surround the ion in a crystal
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Ionic compounds can conduct an electric current when melted or dissolved in water.
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Section 3 Bonding In Metals
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Learning Targets 7.3.1 – I can model the valence electrons of metal atoms – I can describe the arrangement of atoms in a metal – I can explain the importance of alloys.
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Metallic Bonds and Metallic Properties
The valence electrons of metal atoms can be modeled as a “sea” of electrons. Metallic bonds – attraction of the free-floating valence electrons for the positively charged metal atoms.
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Metallic Bonds and Metallic Properties
Good conductors of electrical current because of the free-floating electrons. Malleable (pounded into sheets) Ductile (pulled into wires)
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Crystalline Structure of Metals
Metal atoms are arranged in very compact and orderly patterns. Body-centered cubic (8 neighbors) Face-centered cubic (12 neighbors) Hexagonal close-packed (12 neighbors)
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Alloys Alloy – 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 the component elements.
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Substitutional alloy – components are about the same size and one replaces (substitutes) another.
Interstitial alloy – components are different sizes and smaller fits into the spaces (intercies) of the larger.
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