Chemistry

Crystalline Solids Crystal Lattice ? A 3D array of points where each point has an identical environment. Unit Cell ? The repeating unit (a unit cell is to a crystal, like a ?brick? is in a house). In a given crystal all unit cells are identical. CaF2 Unit Cell Large cation & Large anion r(Cation)/r(Anion) ~0.72 Small cation & Large anion r(Cation)/r(Anion) ~0.3 Cation Anion Anions and cations want to stay in contact with each other, but when the cation becomes much smaller than the anion, anion-anion contacts prevent this. The solution is to lower the coordination number Ionic radii and coordination number Radius Ratio Rules r(cation)/r(anion) Coordination Number Coordination Geometry ? 0.73 8 Cube ? 0.41 6 Octahedron ? 0.22 4 Tetrahedron ? 0.15 3 Trigonal Planar

* Chapter 7 Periodic Properties of the Elements John D. Bookstaver St. Charles Community College Cottleville, MO Lecture Presentation Development of Periodic Table Dmitri Mendeleev and Lothar Meyer independently came to the same conclusion about how elements should be grouped. Development of Periodic Table Mendeleev, for instance, predicted the discovery of germanium (which he called eka-silicon) as an element with an atomic weight between that of zinc and arsenic, but with chemical properties similar to those of silicon. Periodic Trends In this chapter, we will rationalize observed trends in Sizes of atoms and ions. Ionization energy. Electron affinity. Effective Nuclear Charge

Biology 160 Lecture 1 Introduction, Chemistry and Molecules Introductory Concepts for Studying Biology & Science ? Chapter 1 What is science? ? Knowledge gained through careful observation, experimentation and reasoning. ? Science is: ? Explanatory ? Testable ? Reproducible ? Predictive ? Tentative Questions of Science Scientific discoveries create complex questions: ? Ex. Atom ? Should scientists be free to pursue any research? ? Cloning/Stem cell. ? Should government control scientific progress? ? Progression of science. ? Research normally follows a logical progression. ? Interest focuses on problems that impact humanity. The Importance of Publication ? Results of research are submitted for publication. ? peer review by other