Ionic Bonding

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ionic compounds, cations, anions, metallic bonding, octet rule

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Ionic Bonding

  1. 1. Chapter 7 Ionic and Metallic Bonding
  2. 2. Ions <ul><li>Elements within each group of the periodic table behave similarly because they have the same number of valence electrons. </li></ul><ul><li>Valence electrons are the electrons in the highest occupied energy level of an elements atoms. </li></ul><ul><ul><li>Valence electrons determine the chemical properties of an element. </li></ul></ul>
  3. 3. Valence Electrons <ul><li>To find the number of valence electrons in an atom of a representative element, simply look at its group number. </li></ul>
  4. 4. <ul><li>In forming compounds, atoms tend to gain or lose electrons in order to achieve the electron configuration of a noble gas!!! </li></ul>Octet Rule
  5. 5. Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons <ul><li>C would like to </li></ul><ul><li>N would like to </li></ul><ul><li>O would like to </li></ul>Gain 4 electrons Gain 3 electrons Gain 2 electrons
  6. 6. Key Concept <ul><li>Atoms of metals lose their valence electrons. </li></ul><ul><li>Atoms of some nonmetals ten to gain electrons or to share with other nonmetallic elements to achieve a complete octet </li></ul>
  7. 7. Formation of Cations <ul><li>When an atom loses an electron it produces a positively charged ion, or a cation. </li></ul><ul><li>The most common cations are those produced by the loss of valence electrons from metal atoms. </li></ul>
  8. 8. Electron–Dot Structures for Ions <ul><li>Remove electrons for cations </li></ul>Sodium Atomic number 11 1 s 2 2 s 2 2 p 6 3 s 1 1 Valence electron Na Remove electron to form ion Sodium Ion Atomic number 11 1 s 2 2 s 2 2 p 6 3 s 0 Na + Now has full shell with similar electronic configuration to Neon --Stable noble gas configuration
  9. 9. Formation of Anions <ul><li>The gain of negatively charged electrons by a neutral atom produces an anion. </li></ul>
  10. 10. Electron–Dot Structures for Ions <ul><li>Add electrons for anions </li></ul>Chlorine atomic number 17 1 s 2 2 s 2 2 p 6 3 s 2 3 p 5 7 Valence electrons Add electron to form ion Chloride ion atomic number 17 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 8 Valence electrons - Now has full shell with similar electronic configuration to Argon --Stable noble gas configuration Cl Cl
  11. 11. Lewis Dot Structures Mg example 1 s 2 2 s 2 2 p 6 3 s 2 [Ne] 3 s 2 The valence shell is the outermost shell of electrons of an atom. 2 electrons in the valence Shell Mg Use dots to represent Valence Electrons
  12. 12. Electron-Dot Structures <ul><li>Valence electrons represented by dots </li></ul><ul><li>Electron-dot symbols </li></ul><ul><ul><li>– Examples: Na •, •Mg•, … </li></ul></ul>
  13. 13. Ionic Bonds <ul><li>Compounds composed of cations and anions are called ionic compounds. </li></ul><ul><li>Although they are composed of ions, ionic compounds are electrically neutral. </li></ul>The electrostatic forces that hold ions Together in ionic compounds are Called Ionic bonds.
  14. 14. Ionic Bonds: One Big Greedy Thief Dog!
  15. 15. Formula Units <ul><li>A chemical formula shows the kinds and numbers of atoms in the smallest representative unit of a substance. </li></ul><ul><li>Because an ionic compound exists as a collection of positively and negatively charged ions arranged in repeating patterns, its chemical formula refers to a ratio known as a formula unit. </li></ul>
  16. 16. <ul><li>A formula unit is the lowest whole-number ratio of ions in an ionic compound. </li></ul><ul><li>For NaCl the ratio of the ions is 1:1 (one Na + to one Cl - ) </li></ul><ul><li>What is the formula unit for Magnesium Chloride? </li></ul>
  17. 17. Practice, Practice, Practice <ul><li>Use electron dot structures to determine formulas of the ionic compounds formed when </li></ul><ul><li>1. potassium reacts with iodine. </li></ul><ul><li>2. Aluminum reacts with oxygen. </li></ul>
  18. 18. Properties of Ionic Compounds <ul><li>Most are crystalline solids at room temperature. </li></ul><ul><li>High melting points. </li></ul><ul><li>Conduct electricity when melted or dissolved in water. </li></ul>
  19. 19. Practice, Practice <ul><li>Write the formulas for each compound . </li></ul><ul><li>Barium chloride </li></ul><ul><li>Lithium oxide </li></ul><ul><li>Magnesium oxide </li></ul><ul><li>Calcium flouride </li></ul>
  20. 20. 7.3 Bonding in Metals <ul><li>The valence electrons of metal atoms can be modeled as a sea of electrons. </li></ul><ul><li>That is, the valence electrons are mobile and can drift freely from one part of the metal to another. </li></ul><ul><li>Metallic Bonding Animation </li></ul>
  21. 21. Metallic Bonds: Mellow dogs with plenty of bones to go around.
  22. 22. Alloys <ul><li>Mixtures composed of two or more elements, at least one of which is a metal. </li></ul><ul><li>Their properties are often superior to those of their component elements. </li></ul>
  23. 23. Learning Check <ul><li>Give the ionic charge for each of the following: </li></ul><ul><li>A. 12 p + and 10 e - </li></ul><ul><li>1) 0 2) 2+ 3) 2- </li></ul><ul><li>B. 50p + and 46 e- </li></ul><ul><li>1) 2+ 2) 4+ 3) 4- </li></ul><ul><li>C. 15 p + and 18e- </li></ul><ul><li>2) 3+ 2) 3- 3) 5- </li></ul>
  24. 24. Learning Check <ul><li>A. Number of valence electrons in aluminum </li></ul><ul><li>1) 1 e - 2) 2 e - 3) 3 e - </li></ul><ul><li>B. Change in electrons for octet </li></ul><ul><li>1) lose 3e - 2) gain 3 e - 3) gain 5 e - </li></ul><ul><li>C. Ionic charge of aluminum </li></ul><ul><li>1) 3- 2) 5- 3) 3 + </li></ul>
  25. 25. Solution <ul><li>A. Number of valence electrons in aluminum </li></ul><ul><li>3) 3 e - </li></ul><ul><li>B. Change in electrons for octet </li></ul><ul><li>1) lose 3e - </li></ul><ul><li>C. Ionic charge of aluminum </li></ul><ul><li>3) 3 + </li></ul>
  26. 26. Review.. <ul><li>What is a chemical bond? </li></ul><ul><ul><li>Force that holds two atoms together </li></ul></ul><ul><li>What is an ionic bond? </li></ul><ul><ul><li>An electrostatic force that holds oppositely charged particles together in an ionic compound </li></ul></ul><ul><ul><li>Forms when….? </li></ul></ul><ul><li>What are atoms and compounds always trying to achieve? </li></ul><ul><ul><li>Stability </li></ul></ul><ul><ul><li>Complete set of valence electrons… </li></ul></ul>

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