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Chapter 7

Ionic and Metallic Bonding. Chapter 7. Ions. Valence electrons are the electrons in the highest occupied energy level of an elements atoms. Valence electrons determine the chemical properties THE HILL OF OXIDATION NUMBERS. Group # shows the # of Valence Electrons! 1A = 1 2A = 2 Etc.

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Chapter 7

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  1. Ionic and Metallic Bonding Chapter 7

  2. Ions • Valence electrons are the electrons in the highest occupied energy level of an elements atoms. • Valence electrons determine the chemical properties • THE HILL OF OXIDATION NUMBERS

  3. Group # shows the # of Valence Electrons! 1A = 1 2A = 2 Etc.. A bit of a review! Valence Electrons

  4. Octet Rule • In forming compounds, atoms tend to gain or lose electrons in order to achieve the electron configuration of a noble gas!!!

  5. Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons lose 4 electrons • C would like to • N would like to • O would like to Gain 3 electrons Gain 2 electrons

  6. Metals form Cations Nonmetals form Anions Key Concept

  7. Formation of Cations • When an atom loses an electron it produces a positively charged ion, or a cation. • .

  8. Electron–Dot Structures for Ions • Remove electrons for cations Na Sodium Atomic number 11 1s22s22p63s1 1 Valence electron Remove electron to form ion + Na Sodium Ion Atomic number 11 1s22s22p63s0 Now has full shell with similar electronic configuration to Neon --Stable noble gas configuration

  9. The gain of negatively charged electrons by a neutral atom produces an anion. Formation of Anions

  10. Cl Cl Electron–Dot Structures for Ions • Add electrons for anions Chlorine atomic number 17 1s22s22p63s23p5 7 Valence electrons Add electron to form ion - Chloride ion atomic number 17 1s22s22p63s23p6 8 Valence electrons Now has full shell with similar electronic configuration to Argon --Stable noble gas configuration

  11. Lewis Dot Structures The valence shell is the outermost shell of electrons of an atom. Mg example 1s22s22p6 3s2 [Ne] 3s2 2 electrons in the valence Shell Use dots to represent Valence Electrons Mg

  12. Electron-Dot Structures • Valence electrons represented by dots • Electron-dot symbols – Examples: Na•, •Mg•, …

  13. Ionic Bonds • Compounds composed of cations and anions are called ionic compounds. • Although they are composed of ions, ionic compounds are electrically neutral. The electrostatic forces that hold ions Together in ionic compounds are Called Ionic bonds.

  14. Formula Units • Shows the number of atoms in a compound. • Ionic compounds = Formula Units

  15. Most are crystalline solids at room temperature. High melting points. Conduct electricity when melted or dissolved in water. Properties of Ionic Compounds

  16. A formula unit is the lowest whole-number ratio of ions in an ionic compound. For NaCl the ratio of the ions is 1:1 (one Na+ to one Cl-) What is the formula unit for Magnesium Chloride?

  17. Use the criss cross method to determine formulas of the ionic compounds formed when 1. potassium reacts with iodine. 2. Aluminum reacts with oxygen. Practice, Practice, Practice

  18. Practice, Practice • Write the formulas for each compound. • Barium chloride • Lithium oxide • Magnesium oxide • Calcium flouride

  19. 7.3 Bonding in Metals • The valence electrons of metal atoms can be modeled as a sea of electrons. • That is, the valence electrons are mobile and can drift freely from one part of the metal to another. • Metallic Bonding Animation

  20. Alloys • Mixtures composed of two or more elements, at least one of which is a metal. • Their properties are often superior to those of their component elements.

  21. Learning Check Give the ionic charge for each of the following: A. 12 p+ and 10 e- 1) 0 2) 2+ 3) 2- B. 50p+ and 46 e- 1) 2+ 2) 4+ 3) 4- C. 15 p+ and 18e- 2) 3+ 2) 3- 3) 5-

  22. Learning Check A. Number of valence electrons in aluminum 1) 1 e- 2) 2 e- 3) 3 e- B. Change in electrons for octet 1) lose 3e- 2) gain 3 e- 3) gain 5 e- C. Ionic charge of aluminum 1) 3- 2) 5- 3) 3+

  23. Solution A. Number of valence electrons in aluminum 3) 3 e- B. Change in electrons for octet 1) lose 3e- C. Ionic charge of aluminum 3) 3+

  24. Review.. • What is a chemical bond? • Force that holds two atoms together • What is an ionic bond? • An electrostatic force that holds oppositely charged particles together in an ionic compound • Forms when….? • What are atoms and compounds always trying to achieve? • Stability • Complete set of valence electrons…

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