CHEM 1113 Recitation 10 - Periodic Trends and Ionic Bonds (2)

pdf

School

University of Colorado, Boulder *

*We aren’t endorsed by this school

Course

1113

Subject

Chemistry

Date

Jan 9, 2024

Type

pdf

Pages

Uploaded by PrivateUniverse6512

CHEM 1113 Recitation 10 - Periodic Trends and Ionic Bonds INTRODUCTION Periodicity . . . in chemistry and in life Even before you learned about the Periodic Table of the Elements, you were familiar with other real-world examples of periodicity. The seven days of the week repeat themselves month after month, year after year. Throughout the semester, “Tuesday” conjures up some sort of schedule for you, whether that’s the day you attend chemistry lab or volunteer at the animal shelter or sleep in until noon. There’s a repeatability to your weekly schedule— you can predict some of what you’ll be doing three Wednesdays from now, even if your entire day isn’t yet planned. Other examples of periodicity include the lunar cycle (28-day average), and the Chinese zodiac, which has a 12-year cycle. If you were born in 1964, or 1976, or 1988, or 2000, you were born in the Year of the Dragon. By now, you’re beginning to understand how the Periodic Table of Elements is organized and how you can use it to make predictions of properties of elements that are in the same group or period. It was this repeating of patterns that allowed Dmitri Mendeleev to leave gaps in his original table where he predicted the existence of elements that were not yet discovered. Other ways of organizing the Periodic Table have been developed; one is given here. How does this organization compare to that of the traditional organization? In what ways is it a more useful approach to present the periodic properties of the elements? In what ways is it less useful? Cr edits: Chinese zodiac:http://zodiac-gallery.blogspot.com/2009/10/chinese-zodiac-signs-with-image-chinese.html Spiral Periodic Table: http://chemlab.pc.maricopa.edu/periodic/spiraltable.html

Part I: Periodic Trends of the Elements Using only the Periodic Table, make predictions about properties such as atomic size and to determine electron configurations for atoms and ions. For this section, consider these six elements: O F Mg P Ar K Description Highlight ALL that apply, or “None of these” Support your answers. 1. Its atomic radius is larger than a sulfur atom. O F Mg P Ar K None of these 2. Its most stable ion: (a) has the same electron configuration as neon, and (b) has a larger radius than neon. O F Mg P Ar K None of these 3. Its atoms are diamagnetic ( not attracted by a magnetic field). O F Mg P Ar K None of these 4. Its atoms have five valence electrons. O F Mg P Ar K None of these 5. Its graph of successive ionization energies: O F Mg P Ar K None of these 6. What is the correct arrangement of the following atoms in order of increasing IE 1 (first ionization energy): Ba, Cs, and F. Give a brief explanation of your choice. a) Ba < Cs < F b) Cs < Ba < F c) F < Cs < Ba d) F < Ba < Cs

Part II: Ionic Bonds Earlier in the semester you used solubility rules to decide if a substance would dissolve in solution. Now you can explore why NaOH is soluble and Al(OH) 3 is insoluble. The key to this concept is Lattice Energy. Lattice Energy - the enthalpy change that occurs when 1 mol of an ionic solid is formed from the gaseous ions. Or in terms of a chemical equation, it is the value of ΔH for the following reaction. Na + ( g ) + Cl - ( g ) → NaCl( s ) The value of ΔH Lattice tells us something about the stability of the ionic solid. The more energy released when the ions come together (↑|ΔH Lattice |), the more tightly the solid is held together. 1. If the lattice energy is related to the energy of attraction of oppositely charged particles, then predict how the following might influence the value of the lattice energy: o Magnitude of the charge of the ion o Distance between the ions in the solid 2. Based on your answers above, explain the data in this table: Compound Lattice Energy Solubility NaOH -900 kJ/mol 420 g/L Mg(OH) 2 -3006 kJ/mol 0.009 g/L 3. Predict which compound would have the highest melting point. Explain. 4. Arrange the following compounds in order of decreasing magnitude of lattice energy (most energy released to least energy released when the solid is formed): MgS, NaCl, NaF, MgO Explain your reasoning.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Part III. Lattice Energy Practice 1. Use the following table to rank the compounds in order of decreasing (strongest to weakest) lattice energy. Cation Anion Bond length (pm) M 2+ A 2 – 204 M 2+ B 2 – 192 M + C – 215 2. The bar graph represents the lattice energy of four compounds: KBr, KF, KCl, and MgCl 2 . Match each bar to its ionic compound.

Part IV: Periodic Trends Puzzle On the planet, Periodus, located on an outer spiral arm of the Milky Way opposite from Earth, there are 19 known, naturally-occurring elements. The inhabitants, the Periodicans, have identified the properties of these elements but, since there are only 19 of them, the Periodicans have not bothered to arrange them in an orderly, informative manner like the Periodic Table on Earth. On your visit with the Periodicans, you fondly recalled your enlightening general chemistry experience and the wonders of the periodic table. You describe to them the magic of the periodic table and the vast insight to an element’ s properties as revealed by its mere position on the table. You have generously offered to arrange the 19 Periodican elements into a table. Based on the property/behavior information they have provided and your knowledge of the periodic table for Earth’s e lements, arrange the 19 Periodus elements in the table framework below. Periodican Elements and Their Properties: 1. Element Ar has a 1s 1 electron configuration. 2. Elements Or, Me, and R form – 1 anions. Element Or has a greater electron affinity value than Me but a smaller electron affinity value than element R. 3. Elements Te, Es, T, and N are listed in order of increasing ionization energy. These elements comprise the group of elements that form the +1 cations. 4. Elements Nt, I, At, Is, and Go compose the group of inert (noble) gases and are listed in order of decreasing size. 5. Elements E, He, and Fa have an outer shell configuration of n s 2 and tend to form +2 cations. The atomic number of Fa is higher than that of He but is lower than that of E. 6. Elements Pi, V, and Le are transition metals and are listed in order of increasing atomic radius. This puzzle was adapted from an article in Journal of Chemical Education; original citation is currently not available.