nuclear chemistry “bravo” test 1954 – 15,000 kilotons
TRANSCRIPT
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Nuclear Chemistry
“Bravo” Test 1954 – 15,000 kilotons
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Radioactivity and Nuclear Energy
Objective: To learn the types of radioactive decay Objective: To learn to write nuclear equations that describes radioactive decay Objective: To learn how one element may be changed into another by particle bombardment
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What makes an atom radioactive?Radioactivity: the spontaneous decomposition of a nucleus to form another nucleus and produce one or more particles. -the neutrons act as glue holding the nucleus together-the heavier the atom, the more likely it is to be radioactive-if the number of protons in the nucleus exceeds 83, then the nuclide is radioactive
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Types of Radioactive Decay
alpha production ( , a He): helium nucleus
beta production ( , b e):
gamma ray production (g):
ThHeU 23490
42
23892
234 234 090 91 1Th Pa e
0023490
42
23892 2 ThHeU
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Specifying Isotopes
5
XA
Z
X = the symbol of the element
A = mass number (protons + neutrons)
Z = the atomic number (number of protons)
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Nuclear Symbols
Element symbol
Mass number, A (p+ + no)
Atomic number, Z(number of p+)
U23592
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Key to Understanding Nuclear Reactions
In nuclear reactions, both the atomic number Z and the mass number A must be conserved
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Balancing Nuclear Equations
226 488 2Ra
226 = 4 + ____222
222
88 = 2 + ___86
86
Atomic number 86 is radon, Rn
Rn
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Alpha Decay
Alpha production (a):
an alpha particle is a
helium nucleus238 4 23492 2 90U He Th
Alpha decay is limited to heavy, radioactive
nuclei
238 4 23492 2 90U Th
4 2 4 22 2He or
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Alpha (α) Decay
E1
P+N
P P-2 + He
4
2 E2
P+N -4
an alpha particle (helium nucleus) is produced
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Alpha Radiation
Limited to VERY large nucleii.
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Example of Alpha Decay
Ra222
88 86+ He
4
2 Rn
Radium 222 decays by α particle production to Radon 218
218
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Beta Decay
Beta production (b):A beta particle is an electron ejected from the nucleus
234 234 090 91 1Th Pa e
Beta emission converts a neutron to a proton
234 234 090 91 1Th Pa
0 01 1e or
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Beta (β) Decay
Beta emission converts a neutron to a proton
E1
P+N
P P+1 + e0
-1 E2
P+N
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Beta Radiatio
n
Converts a neutron into a proton.
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Example of Beta DecayNotice the mass of the beta particle is zero; it is so small that is must be neglected.
C14
6 7 + e0
-1 N
14
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Example of Beta Decay
Th234
90 91 + e0
-1 Pa
234
Thorium 234 decays by β particle production to Protactinium 234
(notice: no change in mass number A, and an increase of 1 in atomic number Z)
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Gamma Ray Production
Gamma ray production (g):
Gamma rays are high energy photons produced in association with other forms of decay.
Gamma rays are massless and do not, by themselves, change the nucleus
0023490
42
23892 2 ThHeU
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Gamma Ray Production
Gamma ray production (g):
Gamma rays are high energy photons produced in association with other forms of decay.Gamma rays are massless and do not, by themselves, change the nucleus
0023490
42
23892 2 ThHeU
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Positron Production
Positron emission:Positrons are the anti-particle of the electron
Positron emission converts a proton to a neutron
NeeNa 2210
01
2211
e01
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Positron Production
E1
P+N
P P-1 + e0
1 E2
P+N
Positron emission converts a proton to a neutron
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Electron Capture
Electron capture: (inner-orbital electron is captured by the nucleus)
Electron capture converts a proton to a neutron
0020179
01
20180 AueHg
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Alpha Particle Emission
Beta Particle Emission
Gamma Ray Emission
Symbol or or
Mass Heavy Light No Mass
How it changes the
nucleus
Decreases the mass number by 4
Decreases the atomic number by 2
Converts a neutron into a proton
Increases atomic number by 1
No change to the nucleus
Penetration Low Medium High
Protection provided by…
Skin Paper, clothing Lead
Danger Low Medium High
242He
242 e01 01 00
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Types of Radiation
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NuclearStability
Decay will occur in such a way as to return a nucleus to the band (line) of stability.
The most stable nuclide is Iron-56
If Z > 83, the nuclide is radioactive
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A Decay Series
A radioactive nucleus reaches a stable state by a series of steps
Graphic – Wikimedia Commons User Tosaka
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Alpha Particle Emission
Beta Particle Emission
Gamma Ray Emission
Symbol or or
Mass Heavy Light No Mass
How it changes the
nucleus
Decreases the mass number by 4
Decreases the atomic number by 2
Converts a neutron into a proton
Increases atomic number by 1
No change to the nucleus
Penetration Low Medium High
Protection provided by…
Skin Paper, clothing Lead
Danger Low Medium High
242He
242 e01 01 00