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test mod. 13

science

QuestionAnswer
(Each definition is worth 6 points)Define: Nucleus The center of an atom, containing the protons and neutrons
Define: Atomic number The number of protons in an atom
Define: Mass number the sum of the numbers of neutrons and protons in the nucleus of an atom
Define: Isotopes Atoms with the same number of protons but different numbers of neutrons
Element A collection of atoms that all have the same number of protons
Radioactive isotope An atom with a nucleus that is not stable
1 (pt)Which is larger, a proton or an electron? Proton
(1 pt) Which of the 2 above is negatively charged? Electron
(1 pt-1/2 for each answer) What causes the nuclear force? Why can this force act only over very short distances? The nuclear force is caused by the exchange of pions. It is a short-range force because pions can only exist for a short time.
(3 pts - 1 for each answer) List the number of protons, neutrons, and electrons in the following atoms: (48)Ca_____,____,____.(124)Sn____,_____,______(109)Ag____,_____,______ Ca- 20 protons, 20 electrons,the mass no. is the sum of the protons and neutrons in the nucleus, thus 28 neutrons.Sn-50 ,50 , 74. Ag-47 protons, 47 electrons. 62 neutrons.
(2 pts.- 1/2 for the correct no. of protons, 1/2 correct no. of neutrons and 1 for the correct arrangement of electrons)Draw an illustration of what the Bohr model says a (23)Na atom looks like. Study, trace and recreate the drawing in the book.
(1 pt. 1/2 for each answer) Which of the following atoms are isotopes?(144)Ce, (144)Nd, (144)Sm, (145)Nd The ones with the same chemical symbol but different mass numbers. (144)Nd, (145)Nd are isotopes.
(1 Pt.) A radioactive isotope has a half-life of 3 hours. If a scientist has 30 grams of the isotope, how much is left after 15 hours? (You may use a calculator) In 1st 3 hrs., the 30 gram sample is reduced to 15 grams. Next 3 hrs., reduced to 7.5 grams. Next 3 hours, reduced to 3.75 grams. Next 3 hrs. reduced to 1.875 gr. Next 3 hrs., reduced to 0.9375 grams.
(1pt) What is the daughter product in the beta decay of (144)Ce? (144)Ce has 58 protons according to the chart. This means there must be 86 neutrons. In beta decay, neutron turns into a proton. Will result in an atom with 59 pro. and 85 neutrons, or (144)Pr.
(1 pt) What is the daughter product in the alpha decay of (220)Rn? (220)Rn has 86 protons, means there must be 134 neutrons. In alpha decay, nucleus loses 2 protons and 2 neutrons. Results in atom with 84 protons and 132 neutrons, or (216)Po.
(1 pt) What is the daughter product in the gamma decay of (239)U? In gamma decay, the no. of protons and neutrons is unaffected by the decay. Thus, the daughter product is the same as the original (239)U.
(1 pt) If a piece of paper is placed between a radioactive isotope and a person, which kind of radioactive particle will the person be protected from? Only from Alpha particles.
Extra Credit: (7 pts) Complete and correct the Summary Oh, you did : ) It is worth 7 of most of these questions.
Created by: debra short
 

 



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