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hw 4 - baum(awb464 H04 Atomic Theory 2 Mccord(50970 This...

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baum (awb464) – H04: Atomic Theory 2 – Mccord – (50970) 1 This print-out should have 30 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 3) 10.0 points What is the principal quantum number for the orbital 3 d ? 1. 2 2. 3 correct 3. None of these 4. 4 5. 5 6. 6 Explanation: n = 3 002 (part 2 of 3) 10.0 points What is the orbital angular momentum quan- tum number for the orbital 3 d ? 1. None of these 2. 2 correct 3. 3 4. 4 5. 1 6. 0 Explanation: = 2 003 (part 3 of 3) 10.0 points How many magnetic quantum numbers does the orbital 3 d have? 1. 7 2. None of these 3. 9 4. 1 5. 3 6. 5 correct Explanation: m = - 2 , - 1 , 0 , 1 , 2 004 10.0 points How many total nodal planes are present in the complete set of 3 d orbitals? 1. 3 2. 10 3. 20 4. 8 correct 5. 16 6. 5 Explanation: There are 5 orbitals in the 3 d set. 4 of those orbitals are cloverleaf-shaped and have 2 nodal planes each. That combines to give 8 total nodal planes for the set. The other (5th) orbital is the d z 2 orbital which has 2 nodal cones, not planes. 005 10.0 points How many nodes are present in a 3 s and a 3 p orbital, respectively? 1. 1 and 1 2. 2 and 2 correct 3. 2 and 1 4. 0 and 1 5. 0 and 2
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baum (awb464) – H04: Atomic Theory 2 – Mccord – (50970) 2 Explanation: A node is a point, a plane or a three dimen- sional region of space where the sign of the wavefunction changes from positive to nega- tive, (or negative to positive) so it equals zero. The lowest energy s orbital is 1 s , and this has no nodes – the wavefunction is always posi- tive. As we go to the next higher value of n we add a spherical node, so 2 s would have one node, and 3 s two. The lowest energy p or- bital is 2 p ; it has one nodal plane which cuts through the nucleus (the two ’lobes’ have op- posite signs). Again, as we go to the next higher value of n we add a spherical node, so a 3 p orbital has two nodes. 006 10.0 points The transition metals are elements with par- tially filled 1. p subshells. 2. d subshells. correct 3. s subshells. 4. f subshells. Explanation: In transition metals, d orbitals are being filled. 007 10.0 points An element with 20 protons and 20 electrons gains one electron. The electron goes into what type of orbital? 1. 4 s 2. 3 s 3. 3 d correct 4. 3 p 5. 4 d 6. 4 p Explanation: This element has electron configuration [Ar] 4 s 2 . The next electron goes into the 3 d orbital according to the Aufbau principle. 008 10.0 points Which element is predicted to have the ground-state electron configuration [He] 2 s 2 2 p 2 ? 1. hydrogen 2. helium 3. lithium 4. nitrogen 5. beryllium 6. carbon correct 7. neon 8. boron 9. oxygen 10. fluorine Explanation: Remembering the noble gas shorthand, count all of the superscripts that appear in the electron configuration. This will give the number of electrons which in a neutral atom
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