Atomic Structure and Nuclear Chemistry PRACTICE Test Name:

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Damon Parsons
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1 Atomic Structure and Nuclear Chemistry PRACTICE Test Name: Chemistry, Mr. Williamson Due Monday Jan 30 th I. Defining Terms Use your notes and your understanding of the atom to determine the term for each of these definitions. You will be given a word bank for the test. alpha beta proton neutron electron _nucleus _orbits isotope _ion anion cation A. This type of particle is emitted from an unstable nucleus. It is made of 2 protons, 2 neutrons and no electrons. B. This type of particle is emitted from an unstable nucleus. It is made when a neutron splits into two pieces, a proton that remains in the nucleus and this particle that is ejected from the nucleus. C. This sub-atomic particle has a mass of 1 amu. It has a positive electrical charge. D. This sub-atomic particle has a mass of 1 amu and has no electrical charge. E. This sub-atomic particle has a negative charge and 1/2000 th of an amu for a mass F. This is the location in the atom where the two sub-atomic particles that have mass are located. G. This is the location in the atom where the electrons are theoretically located according to Niels Borh. H. This term describes an individual atom of an element with a different number of neutrons in the nucleus than another atom of the same element I. Any charged particle J. Any particle that has fewer protons than electrons K. Any particle that has more protons than electrons II. Multiple Choice Answers: Record your answers for the Multiple Choice questions at the end of this test: 1) _C_ 2) _A 3) B 4) _C 5) A 6) C 7) _C_ 8) _B 9) _C_ 10) _B 11) E_ 12) C 13) _E

2 Complete this table. Use these two equations. They will be given on the test, too. Mass = p + + n o Charge = p + - e - Name Symbol Atomic Number Mass Number protons electrons neutrons charge Calcium Ca Uranium Think and Explain Test Questions: use a separate sheet to answer these 1) We have studied different isotopes of elements this fall. There is a metal element that has three naturally occurring isotopes. They are: 126 X, 127 X and 129 X. a. Calculate the average atomic mass of this element given the following: Isotope Percent Abundance 126 X % 126(.55)+127(.2503)+(129)(.1997)= amu 127 X 25.03% 129 X % b. Identify the element from your periodic table: Iodine c. What are the differences between the three isotopes: 126 X, 127 X, and 129 X? There are more protons in 127 (one more) and 129 (three more) than in ) How are Rutherford s nuclear atom and Thomson s plum pudding both ways that scientists have worked to make sense of the world around us? Refer to their data while responding to this question. Rutherford presented data (gold foil expt) that showed that the nucleus is a critical part of the atom. And Thomson s theory about the plum pudding or all mixed up model should be ignored. Particles to exist, but they are more organized. Humans have worked to understand how matter is organized for centuries, both these scientists are working toward improving our understanding.

3 3) John Dalton s Law of definite proportions is over 200 years old. Now that we know about nuclear structure, how come atoms can only combine in simple whole number ratios? (or why can t atoms combine in fractions of atoms?) The atom is defined by the number of protons in its nucleus if an atom is split and at least one proton leaves the nucleus then the element changes! 4) What happens to a nucleus when it undergoes beta decay? A neutron splits into a proton and an electron. The electron is ejected from the nucleus as the beta particle and the proton stays in the nucleus. 5) The half life of Uranium-238 is 4.5 billion years. The half life of uranium-235 is 245,000 years. Which isotope of uranium is more stable? The one with the longer half life, 4.5 million years, is more stable. How can you tell? Half life is the length of time it takes for one half of a sample of radioactive material to decay. The longer the half life, the longer it takes to break down the more stable it is. IV. Nuclear Chemistry: 6) Finish the following these nuclear reactions. ( /16 pts) Write one sentence about any of the reactions after you have completed them Np 91 Pa + 2 _He_ 84 Po 84 _Po+ 0 n a c K -1_β + 20 Ca 6 C + 0 n _N_ β b d. Logical Sentence (something along these lines ) a. An atom of Neptunium-273 goes through an alpha decay to produce an atom of protactinium-233. b. An atom of potassium-39 goes through a beta decay to produce an atom of calcium-39. c. An atom of polonium-211 goes through a neutron decay to produce an atom of polonium-210. d. An atom of carbon-13 is hit by a neutron and then goes through a beta decay to produce an atom of nitrogen ) Explain the law of conservation of mass with respect to nuclear decay. You should refer to one of the four reactions above, or include your own as an example of how mass is conserved in a chemical reaction.the mass of all the particles in a reaction must be maintained. The sum of the atomic mass number s of the reactants must equal the sum of the atomic mass number of the products.

4 Bohr s Atom Complete an appropriate diagram of Bohr s model for these three isotopes. Carbon-13 (atom) Lithium-7 (+1 cation) fluorine-19 (-1 anion) p + = 6_ p + = 3 p + = 9 n o = 7_ n o = 4_ n o = 10_ e - = 6_ e - = 2_ e - = 10_ These diagrams are not to scale. What would an appropriate scale be? SMALL nucleus and tiny electrons floating around in the space outside it. Multiple Choice Questions Select the best answer to these questions in the blanks on the first page of the test. Record your answer neatly and clearly. There is only one best answer for each question. 1) This term is defined by the number of proton plus neutrons in an atom. 2) This term is the difference of the protons and electrons in an atom. 3) This term is the sum of the products of all the relative abundances of the isotopes of an element times their atomic mass number. 4) Which of the following is attributed to Rutherford s work? a. The atom is small b. The atom is divisible c. The atom has a small dense nucleus d. Electrons are organized

5 5) Rank these particles from most massive to least massive: proton, electron, alpha particle, neutron a. Alpha > neutron > proton > electron b. Electron > proton > neutron > alpha c. Alpha > electron > neutron > proton d. Neutron > proton > electron = alpha 6) Where in the atom are the electrons most often found? a. in the nucleus b. as part of neutrons c. outside the nucleus 7) Why do all nuclear reactions need to be balanced? a. Dalton s Law of Definite Proportions b. Democritus s atoms philosophy c. The Law of conservation of mass d. Rutherford s conclusion that atoms have a small dense positive nucleus. 8) How many protons are there in every atom of magnesium? a. 25 b. 12 c. 37 d ) How many neutrons are there in an atom of aluminum-27? a. 27 b. 13 c. 14 d. 1 e. 0 10) How many electrons are there in the +1 cation of potassium? a. 1 b. 18 c. 19 d. 20 e ) What is the atomic mass of a cation of carbon with 7 neutrons and 2 electrons? a. 6 b. 7 c. 10 d. 12 e ) A 100 gram sample of radioactive material is allowed to decay for 5 days. After the fifth day, only 25 grams of the radioactive material is left. How long is the half-life of the sample? a. 5 days b. 4 days c. 2.5 days d. 1 day d days 13) What mass of radioactive material will be left from a 50 gram sample after 10 hours if the half life is 2 hours? a g b. 10 g c g d g e g

9/13/2013. However, Dalton thought that an atom was just a tiny sphere with no internal parts. This is sometimes referred to as the cannonball model.

9/13/2013. However, Dalton thought that an atom was just a tiny sphere with no internal parts. This is sometimes referred to as the cannonball model. John Dalton was an English scientist who lived in the early 1800s. Dalton s atomic theory served as a model for how matter worked. The principles of Dalton s atomic theory are: 1. Elements are made of