Exam 1-solutions - Version 156 – Exam 1 – sparks...

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Unformatted text preview: Version 156 – Exam 1 – sparks – (51150) 1 This print-out should have 29 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Which of the following atoms has the highest electron affinity? 1. Al 2. Ar 3. Si correct 4. P Explanation: Electron affinity is a measure of how readily a neutral atom will accept an electron to form a- 1 ion. The higher the EA, the more read- ily this occurs. “Higher” may mean “more positive” or “more negative” depending on how this has been defined by your profes- sor. The GENERAL trend is that EA will increase from left to right and from bottom to top. However, noble gases do not want to gain electrons since they already have a full octet. Also, since there is a slight increase in stability when a set of p-orbitals is half full, an element which can achieve this by gaining an electron will tend to have a larger electron affinity (but not as large as that of a group VII element). 002 10.0 points A comparison of the electron configurations of nickel (Ni) and copper (Cu) indicates that 1. Cu has two more d electrons and one less s electron than Ni. correct 2. Cu has one more d electron and one more s electron than Ni. 3. Cu has one more d electron and the same number of s electrons as Ni. 4. Cu has two more d electrons and the same number of s electrons as Ni. 5. Cu has one more d electron and one less s electron than Ni. Explanation: The electron configuration for Ni is [Ar] 3 d 8 4 s 2 , whereas the electron configuration for Cu is [Ar] 3 d 10 4 s 1 , which indicates the difference between their electron distribution. Cu has 10 d-electrons in the 3 d orbital while Ni has 8. Similarly, Cu has 1, while Ni has 2 4 s-electrons. 003 10.0 points Which element is predicted to have the ground-state electron configuration [Kr] 4 d 10 5 s 2 5 p 5 ? 1. tellurium 2. tin 3. iodine correct 4. cadmium 5. cesium 6. indium 7. lutetium 8. xenon 9. antimony 10. barium 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 electron is ‘shuffled’ from the ( n- 1) s orbital. Version 156 – Exam 1 – sparks – (51150) 2 004 10.0 points Elements with great electron affinities (large negative values) often have 1. small sizes and high ionization energies. correct 2. large sizes and high ionization energies....
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This note was uploaded on 04/03/2012 for the course CHEM 56920 taught by Professor Sparks during the Spring '12 term at University of Texas.

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Exam 1-solutions - Version 156 – Exam 1 – sparks...

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