NUCLEAR CHEMISTRY
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Transcript of NUCLEAR CHEMISTRY
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NUCLEAR CHEMISTRY
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Discovery of Radiation
Roentgen (1895)
•Discovered a mysterious form of radiation was given off even without electron beam. This radiation could pass through paper and other objects but not dense materials (lead, bone).
•Called them X-rays
•Studied fluorescent materials that glowed when hit with a beam of electrons.
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Becquerel (1896)•Studied fluorescent minerals containing uranium.•Discovered radioactivity by accident on a cloudy day:•Thought that an external source was needed to produce the mysterious radiation.
•Found that uranium emits radiation without external source.
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Thought radioactivity was a property of heavy elements.
Pierre and Marie Curie
During study, discovered new radioactive elements: Polonium and Radium.
Wondered how small mass can give off large amount of energy:
Explained by Einstein with E=mc2.
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•Studied radioactivity and named types of nuclear radiation.
Rutherford
•Discovered that elements decay into other elements after emitting nuclear radiation. Called it Nuclear Decay.•Gold foil experiment revealed that the mass of an atom is concentrated in the nucleus (atom is mostly space)
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Atomic StructureRecall:Atoms – consist of a positively charged nucleus, which has protons and neutrons.
Isotope Symbol # protons # neutrons
Atomic Mass
Mo-101
H-2
C-14
U-238
Bi-210
He-4
H21C146U238
92
Bi21083
He42
Mo10142 42
1
6
92
83
2
59
1
8
146
127
2
101
2
14
238
210
4
Isotope – atoms of the same chemical element that have a different number of neutrons. Each isotope of a given element is designated by the total number of its protons plus its neutrons.
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Nuclear Forces1. Electric repulsion – ________ charge particles
repel each othersame
2. Strong Nuclear Force – causes protons and neutrons to ________ each otherattract
•Stable Nuclei = strong nuclear force is ________ than repulsion force
greater
•Unstable Nuclei = strong nuclear force is ________ than repulsion force
oHave too many or too few neutrons in nucleusoHave more than 83 protons in nucleusoWill undergo radioactive decay to form a more stable nucleus
less
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Nuclear Decay• Why nuclides decay
– need stable ratio of neutrons to protons
He Th U 42
23490
23892
e Xe I 0-1
13154
13153
e Ar K 01
3818
3819
Pd e Ag 10646
0-1
10647
•Transmutation-One element becomes another.
More than 83 protons means that the nuclei is unstable (radioactive)
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He42
Types of Radiation
• Alpha particle ()– helium nucleus paper2+
• Beta particle (-)– electron
e0-1 1-
lead
• Positron (+)– positron
e01 1+
• Gamma ()– high-energy photon 0 concrete
ChargeShielding
00
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Penetrating Ability of Radiation
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Alpha Emission
He Th U 42
23490
23892
parentnuclide
daughternuclide
alphaparticle
Numbers must balance!!
occurs when the nucleus has too many protons which cause excessive repulsion.
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Alpha Emission
U23592Pu239
94 He42
Ex. Plutonium-239 undergoes alpha decay
+
239
Atomic Mass: = 235
4+
94Atomic #: = 92 2+
Masses must be equal = Conservation of mass
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XAZPo21084 He4
2
Ex. Polonium-210 undergoes alpha decay to produce this daughter nuclide
+
Alpha Emission
Atomic Mass: 210
= A 4+
Atomic #: 84 = Z 2+
210
= A4- = 206
84 = Z2- = 82
XAZ = Pb20682
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Beta Emission
e Xe I 0-1
13154
13153
electron
occurs when the neutron to proton ratio is too great.
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XAZPo21084
Ex. Polonium-210 undergoes beta decay to produce this daughter nuclide
+
Beta Emission
Atomic Mass: 210
= A 0+
Atomic #: 84 = Z -1+
210
= A0- = 210
84 = Z1+ = 85
XAZ = At21085
e01-
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e Ar K 01
3818
3819
positron
Positron EmissionOccurs when the neutron to proton ratio is too small.
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XAZPo21084
Ex. Polonium-210 undergoes positron emission to produce this daughter nuclide
+
Positron Emission
Atomic Mass: 210
= A 0+
Atomic #: 84 = Z +1+
210
= A0- = 210
84 = Z1- = 83
XAZ = Bi21083
e01
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Electron Capture
Pd e Ag 10646
0-1
10647
electron
occurs when the neutron to proton ratio in the nucleus is too small.
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XAZPo21084
Ex. Polonium-210 captures an electron to produce this daughter nuclide
+
Electron Capture
Atomic Mass: 210
= A0+
Atomic #: 84 = Z-1+
A = 210
Z = 83
XAZ = Bi21083
e01-
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Gamma Emission
– Emission of high energy electromagnetic wave.
occurs when the nucleus is at too high an energy.
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XAZPo21084
Ex. Polonium-210 undergoes gamma decay to produce this daughter nuclide
+
Gamma Emission
Atomic Mass: 210
= A 0+
Atomic #: 84 = Z 0+
A = 210
Z = 84
XAZ =
00
Po21084
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Write Nuclear Equations!
Write the nuclear equation for the beta emitter Co-60.