L08MetSecBds145s10 - Lecture 8 Metallic Bonding Secondary...

Info icon This preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
ENGR 145: Chemistry of Materials Case Western Reserve University Lecture 8: Metallic Bonding; Secondary Bonding Reading assignment: C&R §2.6-2.7; §12.5-12.6; OGC §10.2-10.3 Learning objectives: Understand metallic bonds as one extreme on the metallic-covalent continuum of bond character Use the bond type triangle to identify the predominant bond type in simple compounds Explain qualitatively how discrete atomic states of free atoms become bands in solids Understand the difference in band structures between metallic solids and semiconductors Describe absorption and emission of photons of the band-gap energy in semiconductors, and applications of these phenomena Recognize the role of secondary bonds in solids hydrogen bonds van der Waals bonds 1 Lecture 8, spring 2010
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
ENGR 145: Chemistry of Materials Case Western Reserve University Covalent vs. Metallic Character Covalent bonding: sharing of electrons The electrons are localized, mostly between the atoms Metallic bonding: sharing of electrons The electrons are distributed throughout the solid or M + M + electron “gas” or “sea” 2 Lecture 8, spring 2010
Image of page 2
ENGR 145: Chemistry of Materials Case Western Reserve University + + e M M loosely bound valence electrons forming a “gas” or a “sea” ion cores (filled shells) Metallic Bonding 3 Lecture 8, spring 2010
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
metallic-covalent bonding spectrum 100% covalent localized electrons A B 100% metallic delocalized electrons A B A B Average of electronegativity χ avg = | χ A + χ B | /2 : increasing χ avg covalent-ionic bonding spectrum 100% covalent 100% ionic A + B - A B A B increasing Δ χ and polarity transfer of electrons sharing of electrons dipole moment Difference in electronegativity, Δ χ = | χ A χ B | : When at least one of the atoms in a bond has high electronegativity: When both atoms in a bond have similar electronegativity: 4
Image of page 4
ENGR 145: Chemistry of Materials Case Western Reserve University Bond Type Triangle increasing χ avg increasing Δ χ C – covalent χ avg large Δ χ small C B – ionic χ avg medium Δ χ large A – metallic χ avg small Δ χ small D – semimetallic B A D 5 Lecture 8, spring 2010 χ avg Δ χ
Image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern