CHEM 123 notes assignments - Crystal Structure Solids are...

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

View Full Document Right Arrow Icon
Chapt. 13 1 Crystal Structure Solids are divided into two categories : Crystalline: Possesses rigid and long-range order. Amorphous: Lacks well-defined arrangement. Structure of a crystalline solid is based on the unit cell, a basic repeating structural unit Classification by Bonding Ionic e.g. NaCl, NH 4 Cl etc Positive and negative ions held in their lattice positions by strong ionic bonds Covalent e.g. diamond, SiO 2 Atoms held in lattice positions by strong covalent bonds Molecular e.g. H 2 O(s), CO 2 (s) Molecules held together by weak intermolecular forces Metallic e.g. Al(s), Fe(s) etc Metal cations held in lattice positions by strong metalic bonds
Image of page 1

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

View Full Document Right Arrow Icon
Chapt. 13 2 Orthorhombic Monoclinic ZrO 2 Cubic Classification Crystalline Solids Simple Body- centered Face- centered Trigonal Body- centered Simple Rhombohedral Hexagonal Simple Base- centered Body- centered Face- centered Simple Base- centered Triclinic Turquoise, birthstone for December, Sky blue to bluish green. The name means "Turkish stone". Turquoise is porous, so contact with liquids, oils or even perspiration should be avoided. Jewelry made with turquoise should be removed before washing hands, etc.. The pure blue color is rare, most stones contain the matrix from which it was found. Although the stones without matrix are rarer and more valuable, many people find the black matrix attractive, and makes the stone unique. Hardness: 5 - 6 Specific Gravity: 2.6 - 2.8 Chemical Composition: CuAl 6 (PO 4 ) 4 (OH) 8 *5(H 2 O), Hydrated Copper Aluminum Phosphate Crystal Structure: Triclinic LiSb 2 AsS KNa 22 (SO 4 ) 9 (CO 3 ) 2 Cl Hanksite Sulfur MnCO 3 Rhodochrosite Calcite CaCO 3 (has many Structures) Pyrite FeS 2
Image of page 2
Chapt. 13 3 A three dimensional array of points designating the centers of the components (Such as atoms, ions or molecules ) that shows the repeating pattern of the crystal Lattice Can you pick out the simplest unit cell? Called the Unit Cell
Image of page 3

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

View Full Document Right Arrow Icon
Chapt. 13 4 Unit Cell It is the smallest unit that, when stacked together repeatedly without any gaps can reproduce the entire crystal. The previous slide showed an example of the simple cubic unit cell. Simple primitive cube Eight equivalent points at the corners of a cube Body Centered Cubic Eight equivalent points at the corners of a cube and one at the centre Another possibility Another possibility Face Centered Cubic Eight equivalent points at the corners of a cube and six on the centre of the cube faces
Image of page 4
Chapt. 13 5 SCATTERING OF X-RAYS BY CRYSTALS ∙ In 19th century crystals were identified by their shape ∙ Crystallographers did not know atomic positions within the crystal ∙ In 1895 Roentgen discovered X-rays ∙ And Max von Laue suggested that crystal might act as a diffraction grating for the X- rays. In 1912 Knipping observed X-Ray Diffraction Pattern ∙ Von Laue gets Noble Prize ∙ Braggs also demonstrated diffraction and formulated a diffraction law. When electromagnetic radiation passes through matter it interacts with the electrons and is scattered in all directions and the waves interfere.
Image of page 5

Info icon This 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