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HW4 Solution

# HW4 Solution - Kim Jin Homework 4 Due 5:00 pm Inst Stacy...

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Kim, Jin – Homework 4 – Due: Sep 24 2007, 5:00 pm – Inst: Stacy Sparks 1 This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. IMPORTANT NOTE that this assignment is DUE ON A DIFFERENT DAY AND TIME than normal to accomodate the upcoming exam. 001 (part 1 of 1) 2 points The atomic number, which orders the ele- ments in the periodic table, has been identi- fied as ? of the atom. 1. the sum of the number of protons and neutrons in the nucleus 2. the number of protons in the nucleus correct 3. the number of neutrons in the nucleus 4. the number of electrons in the nucleus Explanation: The atomic number defines the atom and refers to the number of protons in the atom. The number of protons is constant for all atoms of a given element. The number of neutrons in an atom of a given element varies by isotope. The number of electrons can vary depending on the element and its charge. The sum of the number of protons and neutrons in the nucleus is the atomic mass and varies by isotope. 002 (part 1 of 1) 2 points Give the nuclide symbol for an atom that has mass number 64 and 35 neutrons. 1. 29 64 Gd 2. 64 29 Cu correct 3. 35 64 Cu 4. 35 29 Br 5. 99 35 Br 6. 64 35 Br 7. 29 64 Cu 8. 99 64 Gd 9. 35 64 Gd 10. 64 35 Cu Explanation: The standard nuclide symbol takes the form A Z E where E is the element symbol, A is the mass number (number of protons plus the number of neutrons) and Z is the atomic num- ber (number of protons). If the mass number is 64 and the number of neutrons equals 35, then 64 - 35 = 29 is the number of protons or the atomic number. Cu has an atomic number of 29, so 64 29 Cu is the correct symbol. 003 (part 1 of 1) 2 points Carbon has several isotopes, one of which, with a mass of 14 amu, is radioactive. This isotope has 1. 7 protons and 7 neutrons. 2. 6 protons and 6 neutrons. 3. 8 protons and 6 neutrons. 4. 6 protons and 8 neutrons. correct 5. 6 protons and 7 neutrons. Explanation: Carbon has an atomic number of 6 and therefore has 6 protons. If the atomic mass (the number of p + + the number of n ) is 14 amu then there are 14 - 6 = 8 neutrons in 14 C. 004 (part 1 of 1) 2 points Which isotope has 35 protons, 35 electrons, and 46 neutrons?

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Kim, Jin – Homework 4 – Due: Sep 24 2007, 5:00 pm – Inst: Stacy Sparks 2 1. 35 46 Pd 2. 81 35 Br correct 3. 81 46 Pd 4. 46 35 Br Explanation: The standard nuclide symbol takes the form of A Z E were E is the element symbol, A is the mass number (number p + + number n ), and Z is the atomic number (number p + ). An isotope with 35 protons ( p + ) and 46 neutrons ( n ) has an atomic number of 35 and a mass number of 35 p + + 46 n = 81 amu. Br has an atomic number of 35, so the isotope is 81 35 Br.
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