Practice with Electron Configurations

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Miranda McGee
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1 Practice with Electron Configurations Prelab Assignment Read the entire lab and write an objective and possible hazards in your laboratory notebook. Answer the following questions in your laboratory notebook before coming to lab. You will have to use your textbook and lecture notes to answer these questions. 1. State Pauli s exclusion theory. 2. State the aufbau principle. 3. Describe how the n and l quantum numbers are used in determining the order in which electrons are assigned to orbitals as you move across and then down the periodic table. In other words how are the n and l quantum numbers used to estimate the energy of a subshell. 4. State Hund s Rule. 5. The following is the condensed electron configuration of the element sulfur: [Ne]3s 2 3p 4. Answer the following questions based on this representation for the electron configuration of sulfur. a. Identify what each letter, number, and symbol in the representation of sulfur s electron configuration shown above tells us. b. How many total electrons does the element sulfur have and how can you tell this from the above representation?

2 c. How many valence electrons, or outer electrons that may participate in chemical reactions, does the element sulfur have and how can you tell this from the above representation? d. What period does the element sulfur lie in and how can you tell this from the above representation? e. What group does the element sulfur lie in and how can you tell this from the above representation? 6. The following is the orbital box notation for the electron configuration of the element sulfur: [Ne]. 3s 3p. Answer the following questions based on this representation. a. Identify what each letter, number, and symbol in the representation of sulfur s electron configuration shown above tells us. b. How many total electrons does the element sulfur have and how can you tell this from the above representation? c. How many unpaired electrons does sulfur have and how can you tell this from the above representation? d. Do you expect sulfur to be para- or diamagnetic and why? 7. Sketch the periodic table indicating the locations of the s, p, d and f blocks.

3 Procedure: 1. Depict the condensed electron configurations of the following elements: Li, Be, B, C, N, O, F, Ne, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Kr, Cs, La, Ce, U, Au, Pb, and Rn. Please complete these electron configurations without looking at online sources and then use an on-line source to check your work. Be cautious of online periodic tables. Only use tables consistent with the International Union of Pure and Applied Chemistry, IUPAC recommendation that La and Ac be in the d-block rather than the f-block. You may use websites such as or Figure 6.31 in your e-book to check your work. In order to learn from this lab and be prepared for quizzes and exams you must complete the electron configurations yourself first and then use the web to check your work. If you simply copy the answers from the web you will not be prepared for exams in this course or for entrance exams such as the MCAT, PCAT or GRE. Li B N F K Sc V Mn Co Cu Ga Kr La U Pb Be C O Ne Ca Ti Cr Fe Ni Zn As Cs Ce Au Rn

4 2. The elements Ne, Kr, and Rn are noble gases. Examine the electron configurations you have depicted for these elements. What aspect of their electron configurations do these three elements have in common? How might this common feature in Ne, Kr, and Rn s electron configuration explain the octet rule? 3. You depicted the electron configurations for elements in the 2 nd, 4 th and 6 th rows of the periodic table. Examine your depictions of the electron configurations for the elements in these rows and describe the relationship between elements n value, their row in the periodic table, and their block in the periodic table. In other words what is the relationship between the n value for elements in the s and p block and the row they are in. What is the relationship between the d block elements and the row they are in, and so forth. Also read section 6.9 titled Electron Configurations and The Periodic Table in your e-book. 4. Examine the electron configurations for the elements Cr, Cu, and Au. Do these elements have the electron configurations you expect? How do the electron configurations for these elements differ from the configurations you expected for these elements? Read the section titled Anomalous Electron Configurations in section 6.9 in your e-book.

5 5. Use condensed orbital box notation to depict the electron configurations of the following elements: Li, Be, B, C, N, O, F, Ne, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Kr, Cs, La, Ce, U, Au, Pb, and Rn. Complete these electron configurations without looking at online sources and then use an on-line source to check your work. Be cautious of on-line periodic tables. Only use tables consistent with the International Union of Pure and Applied Chemistry, IUPAC, recommendation that La and Ac be in the d-block rather than the f-block. You may use websites such as or Figure 6.31 in your e-book to check your work. In order to learn from this lab and be prepared for quizzes and exams you must complete the electron configurations yourself first and then use the web to check your work. If you simply copy the answers from the web you will not be prepared for exams in this course or for entrance exams such as the MCAT, PCAT or GRE. Li B N F K Sc V Mn Co Cu Ga Kr La U Pb Be C O Ne Ca Ti Cr Fe Ni Zn As Cs Ce Au Rn

6 6. Examine the electron configurations for the elements Cr, Cu, and Au. Do these elements have the electron configurations you expect? Read the section titled Anomalous Electron Configurations in section 6.9 in your e-book. Explain why these elements do not follow the expected trend. 7. Examine the orbital box and spdf notations for the electron configurations you completed in problems 1 and 5 above. What are the advantages of each type of notation? 8. Li forms the cation Li + while F forms the anion F -. Use the orbital box notations for the electron configurations of Li, F, Li +, and F - to explain why each of these elements forms the ions they do. 9. Cu may form the cations Cu + and Cu 2+. Use the orbital box notations for the electron configurations of Cu, Cu + and Cu 2+ to explain why copper may form both the Cu + and Cu 2+ cations. Note that the elements nickel and zinc commonly form cations with +2 charges.

7 10. Use the orbital box notations for the electron configurations of Cr 3+ and Cr 6+ to predict which cation is more strongly attracted to a magnet.

Electron Configuration. The electron configuration of an atom tells us how the electrons are distributed among the various atomic orbitals.

Electron Configuration. The electron configuration of an atom tells us how the electrons are distributed among the various atomic orbitals. Electron Configuration The electron configuration of an atom tells us how the electrons are distributed among the various atomic orbitals. Spin Quantum Number, m s In the 1920s, it was discovered that