HW3 - Lin (cgl286) Homework 3 Lyon (52370) 1 This print-out...

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Unformatted text preview: Lin (cgl286) Homework 3 Lyon (52370) 1 This print-out should have 30 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. This HW assignment is due Tuesday, Feb. 17, by 11PM. 001 10.0 points A comparison of the electron configurations of cobalt (Co) and chromium (Cr) indicates that 1. Cr has 2 fewer d electrons and one less s electron than Co. correct 2. Cr has 3 fewer d electrons and the same number of s electrons as Co. 3. Cr has 3 fewer d electrons and one more s electron than Co. 4. Cr has 3 fewer d electrons and one less s electron than Co. 5. Cr has 2 fewer d electrons and the same number of s electrons as Co. Explanation: Cr is an exception. It is more stable when it has a half filled d-orbital. One of its 4 s electrons is elevated into the 3 d orbital, giving it one 4 s electron and five 3 d electrons. 002 10.0 points What is the ground-state electron configura- tion expected for vanadium? 1. [Ar] 3 d 5 2. [Ar] 1 s 1 2 p 4 3. [Ar] 3 d 3 4 s 2 correct 4. [Ar] 3 d 4 4 s 1 5. [Ar] 3 d 1 2 s 2 2 p 2 6. [Ar] 4 p 5 7. [Ar] 3 f 5 Explanation: The Aufbau order of electron filling is 1 s , 2 s , 2 p , 3 s , 3 p , 4 s , 3 d , 4 p , 5 s , 4 d , 5 p , 6 s , 4 f , 5 d , 6 p , etc . s orbitals can hold 2 electrons, p orbitals 6 electrons, and d orbitals 10 electrons. Note some exceptions do occur in the electron con- figuration of atoms because of the stability of either a full or half-full outermost d-orbital, so you may need to account for this by shuffling an electron from the ( n- 1) s orbital. Finally use noble gas shorthand to get the answer: [Ar] 3 d 3 4 s 2 . 003 10.0 points Which element is predicted to have the ground-state electron configuration [Ne] 3 s 2 3 p 4 ? 1. phosphorous 2. argon 3. titanium 4. potassium 5. scandium 6. aluminum 7. sulfur correct 8. silicon 9. chlorine 10. calcium 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 is equal to the number of protons (atomic number of the element). Note some excep- tions do occur in the electron configuration of atoms because of the stability of either a full or half-full outermost d-orbital; sometimes an Lin (cgl286) Homework 3 Lyon (52370) 2 electron is shuffled from the ( n- 1) s orbital. 004 10.0 points How many valence electrons are present in the atom Ba? 1. 12 2. 11 3. 7 4. 5 5. 2 correct 6. 6 Explanation: 005 10.0 points Which electron configuration is possible? 1. 1 s 2 2 s 2 2 p 7 2. None of these is possible. 3. 1 s 2 2 s 1 2 p 6 3 s 3 4. 1 s 2 2 s 2 2 p 6 2 d 1 3 s 2 5. 1 s 2 2 s 2 2 p 6 2 d 1 6. 1 s 2 2 s 2 2 p 5 3 s 2 correct Explanation: 2 d 1 is not allowed: = 2 for n = 2, so there is no d subshell....
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HW3 - Lin (cgl286) Homework 3 Lyon (52370) 1 This print-out...

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