PHYS 202: Chapter 26 and 29
48 Cards in this Set
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How many neutrons does a 139I nucleus have?
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8.60×101
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Calculate the binding energy of 12C6 using the data in Table29.2 and the mass of 12C6 is 11178.0MeV. (MeV)
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9.21×101 MeV
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A 224Ra atom (Z=88, Atomic mass = 224.020186 amu) consists of protons (Mass = 1.00728 amu), neutrons (Mass = 1.00867 amu) and electrons (Mass = 0.000549 amu). Calculate the binding energy per nucleon.
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7.68 MeV
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A sample contains 75000 radioactive nuclei. In a time of 3 minutes, 1500 of the nuclei decay. Evaluate the half life of the sample (in minutes).
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1.03×102
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The half life of 14C is 5730 years. What fraction of the 14C nuclei in a sample are left after 8380 years?
The amount of 14C in an old, isolated sample of vegetation is 0.692 that expected from a present day sample with an equivalent carbon content. Calculate the age of the old sample …
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3.63×10-1
3.04×103
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A sample of polonium has a half-life of 2.7 minutes and an initial activity of 8.400×108 Bq. What is its activity after 28 minutes have elapsed?
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6.35×105 Bq
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A nucleus of an atom generally contains:
a) electrons
b) protons
c) neutrons
d) protons and neutrons
e) protons and electrons
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d) protons and neutrons
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Most of the atom is
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empty
space containing the
orbiting electrons
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Z: Atomic number =
A: Mass number =
N: Neutron number =
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number of protons
number of nucleons
number of neutrons
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__ determines the element
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Z
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How many neutrons are in the following isotope? (The isotope may be
uncommon or unstable.) 3
11
Li
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8
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Lithium has two stable isotopes, with the following natural abundances:
92.6% of naturally occurring Lithium is 7Li, with m = 7.016 u
7.5% of naturally occurring Lithium is 6Li, with m = 6.015 u
What is the chemical atomic mass of Lithium?
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(0.0750⇥6.015 u) + (0.926⇥7.016 u) = 6.94 u
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The periodic table lists the mass of
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naturally occurring elements
(isotopes weighted by their natural abundance)
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Boron, with atomic number Z=5, has two stable isotopes, with atomic
mass numbers A=10 and A=11. Boron’s chemical atomic mass is 10.81. What
are the approximate fractions of the two stable boron isotopes found in
nature?
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80% 11B, 20% 10B
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Total mass:
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Z mp +Z me + N mn
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The atom “weighs” less that the sum of its parts. Where is the missing mass?
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A nucleus is bound.
It requires energy to break it apart: binding energy
It requires this energy to break the nuclear bonds.
The energy is given back as mass to its parts
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The nucleus contains protons and neutrons
Protons are positively charged & they repel, right?
What holds the nucleus together?
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The strong nuclear force
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The strong force
e
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- is attractive
- only acts on n & p
- is short range
- is stronger than the
Coulomb repulsive forc
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Unstable nuclei are
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radioactive
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Spontaneous decay based on
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probability
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unit of activity
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bequerel [Bq]
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Each decay corresponds to
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the emission of a particle
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Activity is a measure of
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he radiation given off
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Alpha Decay
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A large unstable nucleus breaks apart loosing 2 neutrons and 2 protons
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Beta Decay
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An unstable nucleus changes its neutron and proton balance
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The physical effects due to the absorption of radiation in matter is
measured as dose. The dose is the amount of _______ deposited by the
absorbed radiation.
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energy
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Gamma Decay
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A nucleus is a quantum system with discrete energy levels. If the nucleus
changes state, a photon is emitted: A gamma ray
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Alpha and Beta decay often leave the daughter nucleus
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in an excited state
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What is the daughter nucleus for this decay: 40K-> +e! + ve
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40Ca
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222Rn -> ?? + alpha
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218Po
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99Tc -> ?? + gamma
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99Tc
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The cobalt isotope 60Co decays to the nickel isotope 60Ni. The decay
process is
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b) Beta minus decay
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Nuclear radiation is
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ionizing radiation: ionizes atoms and breaks molecular
bonds
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Ionizing radiation only interacts with
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electrons in atoms and molecules
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The activity of a radioactive sample only defines
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the rate of particle emission
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The effect of radiation (e.g. biological damage) is due to
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the energy of the
ionizing radiation
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The physical effects due to the absorption of ionizing radiation measured in
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Absorbed Dose (D): in grays
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Greater quality factor means larger
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biological effects
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When matter and antimatter meet,
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they annihilate - their mass is
converting to only energy
The energy is released as two photons in opposite directions
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A positron is
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the anti-matter version of an electron
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P1. Calculate the binding energy and binding energy per nucleon of 9Be
binding energy per nucleon:
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58.165 MeV
6.463 MeV
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The Fukushima Daiichi nuclear disaster of 2011 released 1.3 x 107 Bq of
131I, with half life of 8.0 days.
i) Much more 131I was released during with the Chernobyl accident. Falling
to the ground (grass), 131I was consumed by cows and concentrated into
milk, which was too radioactive t…
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The 131I can decay away while the cheese ages
Milk must be consumed immediately
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The Fukushima Daiichi nuclear disaster of 2011 released 1.3 x 107 Bq of
131I, with half life of 8.0 days.
ii) How long until the 131I activity is reduced to 1% of initial value?
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t = 53 d
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The Fukushima Daiichi nuclear disaster of 2011 released 1.3 x 107 Bq of
131I, with half life of 8.0 days.
iii) How many atoms of 131I were released by Fukushima
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N0 = 1.3⇥1013
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Most of the internal radiation of the human body is due to a single
isotope, the beta emitter 40K, with half life of 1.28×109 years. The body
contains about 140 g of potassium; of this potassium, about 0.012% is 40K.
i) What is the total activity, in Bq, of a human?
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2.53⇥1020 atoms
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Most of the internal radiation of the human body is due to a single
isotope, the beta emitter 40K, with half life of 1.28×109 years. The body
contains about 140 g of potassium; of this potassium, about 0.012% is 40K.
i) What is the total activity, in Bq, of a human?
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4300 Bq
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Most of the internal radiation of the human body is due to a single
isotope, the beta emitter 40K, with half life of 1.28×109 years. The body
contains about 140 g of potassium; of this potassium, about 0.012% is 40K.
ii) Each 40K decay produces a ~ 560 keV beta particle. What dose, and…
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= 1.7⇥10!4Gy
= 0.17 mSv
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dose equivalent unit
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sievert
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PHYS 202: Exam 1