2 T 2. The 2p subshell has a smaller average size than the 3p subshell.

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1 GLY4200C Name 90 points September 16, took exam - Numbers to the left of the question number in red are the number of incorrect responses. Instructor comments are in blue. Florida Atlantic University MINERALOGY -- MIDTERM 1 EXAMINATION KEY True-False - Print the letter T or F in the blank to indicate if each of the following statements is true or false. Illegible answers are wrong. (1 point each) 0 F 1. Specific gravity has the dimensions of g/cm 3 in mineralogy. 2 T 2. The 2p subshell has a smaller average size than the 3p subshell. 0 F 3. Anions are atoms which have gained one or more electrons, and which are positively charged. 1 T 4. Covalently bonded substances are sometimes composed of discrete molecules. 0 T 5. Streak color is a more reliable tool for identification of minerals than is the actual color. 0 F 6. Covalently bonded substances yield ions in aqueous solution. 1 T 7. In the Bohr model of the atom, electrons are distributed in specific orbits of discrete energy levels (AKA shells). 0 F 8. Minerals which display parting always break smoothly along a plane with a particular orientation, which varies from mineral to mineral. Parting is do to defects, which are not always present. This question was thrown out since some students interpreted which display parting as meaning parting was present. 0 T 9. The manner in which elements are held together, the chemical bond, determines many physical properties displayed by minerals. 1 T 10. Mineral identifications are made on the basis of a combination of tests for different properties. No single test, or single, property, is enough to identify a mineral. 0 F 11. Diaphaneity is the reflection of light from a mineral s surface. 0 T 12. In order for a crystal to show the piezoelectric property it must have a polar axis. 3 F 13. When two or more atoms of the same element bond together, a compound is formed. 1

2 0 F 14. Hydrogen bonds have approximately the same strength as ionic or covalent bonds. 5 F 15. Ionic radii increase with increasing oxidation state. 4 F 16. Plots of electron density versus distance between ions in ionically bonded substances have a very narrow minima, making it easy to assign a radius. 1 T 17. As atomic size increases, so do the dispersion forces. 0 T 18. Radii increase on going down a column of the periodic table. 5 F 19. The p subshell has m values of O, +1, or +2. Since l = 1, ml = 0, +1, or -1 7 T 20. In minerals with more than one bond type, it is common for the mineral to have strongly directional properties. See text, page 64 2 F 21. The radius of a low-spin ion will be larger than the radius of a high-spin ion. 2 F 22. Compounds ending in the suffix -ite do not contain oxygen. 2 T 23. Iridescence is caused by interference of light in thin films of different refractive indices and varying thickness. 6 F 24. As the difference in electronegativity between the cation and anion increases, so does the percent covalent bonding between them. The percent ionic bonding increases. 4 T 25. The CN for both tetragonal and square planar configurations is the same, but the radius ratio for the square planar configuration is larger. 3 F 26. All of the rare earth elements have abundances considerably less than lead. 4 T 27. Among ions with identical charge and differing radii, the smaller ions will be incorporated into crystal structures first. This is why garnets show preferential concentration of heavy rare earth elements. Multiple-Choice - Choose the best response to each statement or question. Print the letter corresponding to your choice in the blank. (1 point each) 3 B 1. One nanometer is equivalent to how many centimeters? A B C D

3 6 A 2. The quantum number for a given orbital is two. What letter designates this orbital? A. d B. f C. p D. s 5 A 3. The bonding within the graphene layers in graphite is due to what type of bonds? (Hint: Read question carefully.) Within the layer, not between layers A. Covalent B. Ionic C. Van der Waals D. Metallic 3 A 4. Which quantum number determines the shape of the electronic orbital? A. Azimuthal quantum number, (see text, page 40) B. Magnetic quantum number, m C. Principal quantum number, n D. Spin quantum number, s 3 D 5. How many electrons can be placed in the orbitals described by n = 4, = 3? These are f electrons, and there are 14 electrons in the f shells A. 2 B. 6 C. 10 D A 6. Which type of orbital is being filled across the Second Transition row? A. d B. f C. p D. s 0 B 7. A glass-like luster is: A. Adamantine B. Vitreous C. Resinous D. Pearly 0 D 8. Heat detectors often use which of the following mineral properties? A. Diaphaneity B. Fluorescence C. Magnetism D. Pyroelectricity 3

4 0 D 9. The effective radius of an ion depends on: A. The type of neighboring ions B. The number of neighboring ions C. The charge of the ion D. All of the above 3 B 10. The quantum number which refers to the orientation of the orbital in space. A. B. m C. n D. s 1 A 11. Metals can be drawn into wire. This is an example of which property? A. Ductility B. Malleability C. Tenacity D. All of the above 0 D 12. Collectively, the different types of the atoms of one element are called: A. Isochromes B. Isochrones C. Isoclines D. Isotopes 3 B 13. What type of bonding is responsible for the anonymously high boiling points of water and ammonia? A. Covalent B. Hydrogen C. Ionic D. Metallic 4 C 14. The bond angle in perfect tetrahedral coordination is: A. 180 B. 120 C D C 15. The quantum number which has values 1,2,3... and which refers to the angular momentum of the electron is the: A. Azimuthal quantum number, B. Magnetic quantum number, m C. Principal quantum number, n D. Spin quantum number, s 4

5 11 D 16. According to an 1989 Bureau of Mines report, how many pounds of minerals does the average American use each year? (See text, page 16) A B C. 10,000 D. 40,000 4 D 17. Orbitals belonging to which of the following subshell types are non-directional? A. d B. f C. p D. s 1 C 18.The size of an atom is on the order of: A. One millimeter B. One micrometer C. One angstrom D. One fermi 5 A 19. The left most column in the periodic table is known as: A. Alkali metals B. Alkaline earths C. Halogens D. Nobel gases 2 C 20. What is the coordination number of the Mg 2+ ion in octahedral coordination? A. II B. IV C. VI D. VIII Valance Electrons - List the valence electrons of the following species. ( 1 point each) 5 1. Cl 3s 2 3p Ca 4s 2 3d electrons are not valence electrons here 5 3. Ni 3d 8 4s 2 3d electrons are valence electrons here 5

6 Valance States - List the most common valance states of each of the following ions, unless a particular state is designated. (1 point each) Be sure to include the sign Li Cl Eu (Europous) +2 You need to remember that REE elements are usually 3+, except for Eu, which can be 2+, and that -ous is the lower oxidation state Fill-Ins - Write in the word or words which best completes each statement or answers each question. (1 point per blank) 1-3. In Cornelius Klein s definition of a mineral, four properties were mentioned. Name and briefly describe them, including exceptions, if any. 2 A. OCCUR NATURALLY - SYNTHETIC MATERIALS ARE NOT MINERALS 0.5 B. BE INORGANIC - EXCEPT PERHAPS THOSE FORMED BY BIOMINERALIZATION 5.5 C. HAVE A DEFINITE ATOMIC ARRANGEMENT (CRYSTALLINITY) 3.5 D. SMALL RANGE OF PHYSICAL AND CHEMICAL PROPERTIES - SOME MINERALS HAVE A COMPOSITIONAL RANGE, RATHER THAN A FIXED CHEMICAL COMPOSITION 0 4. The symbol REE stands for RARE EARTH ELEMENTS Elements whose valance electrons may be denoted as ns 2 are called ALKALINE EARTHS The Si-Si distance in silicon metal is 0.234nm. What is the Si radius? nm 5 7. In which CN, (IV, VI, or VIII) would Fe 2+ be larger? VIII See slide 10 of the Radius Determination lecture 3 8. How many significant figures are expressed in the number ? TWO 4 9. Radii decrease on going from left to right across the periodic table. What column of the periodic table is an exception to this rule? 13) THE RADII OF THE INERT OR NOBEL GASES ARE LARGER THAN THE ELEMENTS TO THEIR LEFT. 6

7 Why is this the case? 14) UNLIKE A BALL, AN ATOM DOESN'T HAVE A FIXED RADIUS. THE RADIUS OF AN ATOM CAN ONLY BE FOUND BY MEASURING THE DISTANCE BETWEEN THE NUCLEI OF TWO TOUCHING ATOMS, AND THEN HALVING THAT DISTANCE. SINCE NOBEL GAS ELEMENTS ARE ONLY VERY WEAKLY BONDED TOGETHER, THEY DO NOT COMPRESS LIKE OTHER ELEMENTS DUE, AND THEIR RADII ARE LARGER If n = 4, what are the possible values of m? ±3, ±2, ±1, 0 4! 12. When a mineral is tested with dilute hydrochloric acid, and it effervesces, what gas is released? CARBON DIOXIDE Various answers included oxygen, hydrogen, and chlorine 7

8 Matching - Match the discovery in column one with the person(s) associated with the discovery in column two. Answers may be used once, more than one, or not at all (One point each) Column 1 0 J 1. This Russian chemist said, "The properties of the elements are a periodic function of their atomic masses." 3 M 2. The idea that all four quantum numbers for any two electrons on the same atom cannot be the same was first discovered by this man. 8 N 3. The concept of electronegativity as related to the percent ionic versus percent covalent bond was formulated by this scientist. (See p of text) 1 H 4. French physicist who suggested that, like light, electrons could act as both particles and waves. The waves produced by an electron confined in its orbit about the nucleus sets up a standing wave of specific wavelength, energy and frequency Column 2 A. Georgius Agricola B. Lorenzo Romano Amedeo Carlo Avogadro C. Johann Jakob Balmer D. Niels Henrik David Bohr E. Marie Sklodowska-Curie F. Paul Jacques Curie G. Pierre Curie H. Louis Victor De Broglie I. Fritz Wolfgang London J. Dmitri Ivanovich Mendeleev K. Friedrich Mohs L. Henry G.J. Moseley M. Wolfgang Ernst Pauli N. Linus Carl Pauling O. Erwin Schrödinger P. Nicholas Steno Q. Harold Clayton Urey R. Johannes Diderik van der Waals 8 I 5. The existence of dispersion forces, due to temporary fluctuating electric dipoles, was first suggested as a possibility by this German-American physicist. 3 L 6. This British chemist said, Similar properties recur periodically when elements are arranged by increasing atomic number. 8

9 Discussion questions - Write a complete, concise answer to each of the following questions. Diagrams (labeled) may be used to supplement your written answers, where appropriate. Points as shown 4 1. Discuss Coulomb s Law. Give the equation, and define all symbols used in your equation. (4 points) F (Z 1 Z 2 )/r 2 where F is the force of attraction between ions, Z i = charge on each ion and r is the distance between ions The following compounds have the interionic distances listed. BaO nm CaO nm MgO nm SrO nm The bonding is predominantly ionic. Predict the order in which the compounds would melt. (Rank them 1, 2, 3, 4 where 1 is the lowest melting and 4 the highest melting.) Explain the reason(s) for your choice. (3 points) This is a simple application of Coulomb s Law All compounds are ionic with a 2+ cation and a 2- anion. The formula for the force of attraction is: Z 1 Z 2 /r 2 Since Z 1 and Z 2 are identical in all cases, the only thing that changes is the radius. As the bond distance gets longer, the bond is weaker and melting will occur at a lower temperature. Therefore the predicted order of melting is: 1. BaO (Lowest M.P.) 2. SrO 3. CaO 4. MgO (Highest M.P.) 9

10 9 3. The following compounds have the bond distances listed. Bismite Bi 2 O 3 Bi-O nm Bismuthanite Bi 2 S 3 Bi-S nm Tellurobismuthanite Bi 2 Te 3 Bi-Te nm Predict the order of hardness. Explain your reasoning. (3 points) Another application of Coulomb s Law. This was better, but still should not have seen this many points missed. Observed hardness values Bismite H = 4-5 Bismuthanite H = Tellurobismuthanite H = The cations are the same in all cases. The anions all have charges of -2. So the only difference in the Coulomb s Law equation is the bond distance, which grows larger as the anion gets bigger. Since the r 2 term is in the denominator, the larger bond distance weakens the bond, and the compound will be softer. Bismite has a considerably shorter bond distance, so would be expected to have considerable stronger bonds, reflected in its moderate hardness. Tellurobismuthanite, with the largest bond distance, would have the weakest bonds and should be the softest. Since the bond distance for Bismuthanite is close to Tellurobismuthanite, we would not expect a large difference in hardness, and this is observed. 10

11 Problems - Do each of the following problems. Show all work. Label answers, including units, if any. Express answers to the correct number of significant figures. List any formula used, and defined all symbols used in the formula. Miraculous answers, unsupported by all necessary calculations, will receive little or no credit Calculate the density of chalcopyrite (CuFeS 2 ) from the following data: (6 points) a = nm c = nm Tetragonal Z = 4 NOTE: In the tetragonal system, to cell edges, a and b, are identical. The third dimension, c, is different. Atomic weights Cu = N = x Fe = S = The answer should be in g/cm 3 M = ( (32.064) = V = (0.525) 2 x (1.032) = nm 3 = x cm 3 11

12 2 2. Calculate the specific gravity of a mineral whose weight in air is 2.47 grams and whose weight in water is 1.98 grams. (3 points) G WA WA W W Where W A = weight in air, and W W = weight in water The mineral hessite, Ag 2 Te, has a density of 8,270 kg/m 3. Express this density in g/cm 3. (2 points) 3 3 kg , m x g m g x kg 10 cm cm

13 Midterm 1 Results 89.5 A A B B MEAN = 73.6 (81.8%) MEDIAN = B C C 50.0 F 13

14 Previous Years Results - Midterm 1-4 th out of 24 Term, Year Mean (percent) Fall, Fall, Fall, Fall, Fall, Fall, Fall, Fall, Spring, Fall, Fall, Fall, Spring, Fall, Spring, Spring, Fall, Fall, Fall, Fall, Fall, Fall, Fall, Fall,