Name CHEM 115 Practice - Quiz #2 Fall 2007 Circle the correct answer to each question. (numbers 1 - 6, 2 points each) 1. Which of the following types of electromagnetic radiation has the lowest frequency (remember, low frequency also means low energy)? a. visible b. ultraviolet c. infrared d. x-rays e. radiowaves 2. Which of the following elements should have the most favorable electron affinity. a. S b. P c. K d. Li e. C 3. Which of the following elements should have the lowest ionization energy? a. Se b. Na c. Cs d. O e. C 4. An orbital (or subshell) quantum number of 2 is which type of orbital? a. s b. p c. d d. f e. none of these 5. Which of the following electron configurations is not allowed by the Pauli exclusion principle? a. 1s22s22p2 b. 1s22s22p63s23p1 c. 1s22s22p63s23p4 2 2 6 2 6 d. 1s 2s 2p 3s 3p e. none of the above 6. Which of the following is NOT ISOELECTRONIC with the others? + 2+ 3- 2- - a. Li b. Mg c. N d. O e. F Solve the following problems. Show all your work, always show your units, and express your answers in the proper number of significant figures. (8 points) 7. a. Electromagnetic radiation with frequency = 9.00 x 10+15 Hz has a wavelength = ? nm . +8 (c = 3.00 x 10 m/s) c 3.00x10+8 m/s -8 νλ = c, so λ = /ν λ = /9.00x10+15 Hz = 3.33x10 m, 33.3 nm b. What is the energy in Joules of this radiation? (h = 6.626 x 10-34 Js) E = hν = (6.626 x 10-34 Js)*( 9.00 x 10+15 s-1) = 5.96x10-18 J (5 points) 8. Discuss the Pauli Exclusion Principle in terms of the significance of determining the electronic configuration of atoms and / or ions. The Pauli Exclusion Principle was postulated in an attempt to explain some of the properties of electrons in an atom. This principle says that in a closed system no two electrons can have the same state (i.e. the state of each electron in any given atom or ion must be represented by a unique set of quantum numbers, QN). Since the first three of our QN represent an orbital, we find that NO MORE THAN TWO electrons can reside in any given orbital AND when two electrons are present, their spins must be paired. 2 (10 points) 9. Use the energy diagrams provided below to show the ground state electron configurations for the species shown. Also, follow the directions under each diagram. 4p 4p 4s 4s 3d 3d 3p 3p 3s 3s 2p 2p 2s 2s 1s 1s a. Place the electrons for Zn in this diagram. a. Place the electrons for Zn2+ in this diagram. b. Write the short form of the electron b. Write the short form of the electron configuration for Zn here: configuration for Zn2+ here: [Ar]3d104s2 [Ar]3d10 (10 points) 10. a. Write the electron configuration for the following two species (you may use the shorter version . you know, the one that will start with [Ar]): Cu [Ar]3d104s1 Cu2+ [Ar]3d9 b. Discuss the meaning of Hund’s rule. Every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin. c. Identify Cu as being either paramagnetic or diamagnetic. Do the same for Cu2+. Cu and Cu2+ are both paramagnetic (they each have an unpaired electron) d. Which electron(s) has(have) the highest energy in Cu? The 4s electron is the highest energy electron in Cu. e. Which is larger Cu or Cu2+? Explain your choice. Cu is larger than Cu2+. Cu2+ has two electrons less than the Cu atom but these electrons are still attracted to the same nuclear charge of +29. .