1 / 18

CHAPTER 2:

CHAPTER 2:. Atomic Structure and Interatomic Bonding. ISSUES TO ADDRESS . • What promotes bonding?. • What types of bonds are there?. • What properties are inferred from bonding?. BOHR ATOM. Nucleus: Z = # protons. = 1 for hydrogen to 94 for plutonium. N = # neutrons.

shaquille
Download Presentation

CHAPTER 2:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CHAPTER 2: Atomic Structure and Interatomic Bonding Dr. Mohammad Abuhaiba

  2. ISSUES TO ADDRESS... • What promotes bonding? • What types of bonds are there? • What properties are inferred from bonding? Dr. Mohammad Abuhaiba

  3. BOHR ATOM Nucleus: Z = # protons = 1 for hydrogen to 94 for plutonium N = # neutrons Atomic mass A ≈ Z + N Dr. Mohammad Abuhaiba

  4. ELECTRON ENERGY STATES Electrons... • have discrete energy states • tend to occupy lowest available energy state. Dr. Mohammad Abuhaiba

  5. STABLE ELECTRON CONFIGURATIONS Stable electron configurations... • have complete s and p subshells • tend to be unreactive. Dr. Mohammad Abuhaiba

  6. SURVEY OF ELEMENTS • Most elements: Electron configuration not stable. Dr. Mohammad Abuhaiba

  7. THE PERIODIC TABLE • Columns: Similar Valence Structure Electropositive elements: Readily give up electrons to become + ions. Electronegative elements: Readily acquire electrons to become - ions. Dr. Mohammad Abuhaiba

  8. ELECTRONEGATIVITY • Ranges from 0.7 to 4.0, • Large values: tendency to acquire electrons. Smaller electronegativity Dr. Mohammad Abuhaiba Larger electronegativity

  9. IONIC BONDING • Occurs between + and - ions. • Requires electron transfer. • Large difference in electronegativity required. • Example: NaCl Dr. Mohammad Abuhaiba

  10. EXAMPLES: IONIC BONDING Give up electrons Acquire electrons Dr. Mohammad Abuhaiba

  11. COVALENT BONDING • Requires shared electrons • Example: CH4 C: has 4 valence e, needs 4 more H: has 1 valence e, needs 1 more Electronegativities are comparable. Dr. Mohammad Abuhaiba

  12. EXAMPLES: COVALENT BONDING • Molecules with nonmetals • Molecules with metals and nonmetals Dr. Mohammad Abuhaiba • Elemental solids (RHS of Periodic Table) • Compound solids (about column IVA)

  13. METALLIC BONDING • Arises from a sea of donated valence electrons (1, 2, or 3 from each atom). • Primary bond for metals and their alloys Dr. Mohammad Abuhaiba

  14. SUMMARY: BONDING Type Bond Energy Comments Ionic Large! Nondirectional (ceramics) Variable Directional Covalent large-Diamond semiconductors, ceramics small-Bismuth polymer chains) Variable Metallic large-Tungsten Nondirectional (metals) small-Mercury Dr. Mohammad Abuhaiba

  15. PROPERTIES FROM BONDING: TM • Melting Temperature, Tm • Bond length, r • Bond energy, Eo Tm is larger if Eo is larger. Dr. Mohammad Abuhaiba

  16. PROPERTIES FROM BONDING: E • Elastic modulus, E • E ~ curvature at ro E is larger if Eo is larger. Dr. Mohammad Abuhaiba

  17. PROPERTIES FROM BONDING: a • Coefficient of thermal expansion, a • a ~ symmetry at ro a is larger if Eo is smaller. Dr. Mohammad Abuhaiba

  18. SUMMARY: PRIMARY BONDS Ceramics Large bond energy large Tm large E small a (Ionic & covalent bonding): Variable bond energy moderate Tm moderate E moderate a Metals (Metallic bonding): Polymers Directional Properties Secondary bonding dominates small T small E large a (Covalent & Secondary): Dr. Mohammad Abuhaiba

More Related