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Review: Common Metal Structures

Review: Common Metal Structures. hcp. bcc. ccp (fcc). ABCABC. not close-packed. ABABAB. Features Filled outer shells  spherical atom cores, isotropic bonding Maximize number of bonds  high coordination number High density. Ionic Bonding & Structures.

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Review: Common Metal Structures

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  1. Review: Common Metal Structures hcp bcc ccp (fcc) ABCABC not close-packed ABABAB • Features • Filled outer shells  spherical atom cores, isotropic bonding • Maximize number of bonds  high coordination number • High density

  2. Ionic Bonding & Structures Isotropic bonding; alternate anions and cations Which is more stable?  – – – – – – + – – + – – – – – – – + – – – Just barely stable

  3. central atom drawn smaller than available space for clarity http://www.chem.ox.ac.uk/icl/heyes/structure_of_solids/Lecture3/Lec3.html#anchor4

  4. Radius Ratio Rules Consider: CN = 6, 8 12

  5. rc + RA 2RA rc + RA 2RA Octahedral Coordination: CN = 6 a

  6. 2(rc + RA) 2RA Cubic Coordination: CN = 8 a

  7. 2RA rc + RA Cuboctahedral: CN = 12 rc + RA = 2RA rc = RA rc/RA = 1

  8. Radius Ratio Rules if rc is smaller than fRA, then the space is too big and the structure is unstable

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