Transcript Nuclear Chemistry

Nuclear Chemistry
Chemical
Nuclear
• Involve electrons
• Affected external
factors (temp,
pressure, catalyst)
• Involve the nucleus
• Release WAY more
energy
• Not affected by
external factors
• Release about a
million times more
energy than chemical
rxns.
Reactions
• Interaction between charged particles
• like charges repel
• opposite charges attract
Electrostatic force
How does the nucleus
stay together?
• Attractive force that acts between all
nuclear particles that are extremely
close together
• Keeps the nucleus together
• Much stronger than electrostatic
force!
Strong Nuclear Force
• The emission (and transmission)
of energy through space in the
form of waves or rays
Radiation
Alpha
4α
2
Beta
0
β
-1
(electron)
Gamma
Radioactivity
0
0
γ
Neutron
1
0
n
Proton
1p
1
•Contain two protons and two neutrons
(A helium nucleus)
•Symbol:
•Carry +2 charge
•Least penetrating form of radiation
(only travels a few centimeter in the air)
•Blocked by paper
Radioactivity-Alpha
• Fast moving electrons
• Symbol:
• Charge: −1
• medium penetration
• (blocked by metal foil or wood)
Radioactivity-Beta
• High energy: waves or rays that possess no
mass
• Symbol:
• Charge: none
• Most penetrating and damaging type of
radiation
• not completely blocked by lead or concrete
Radioactivity-Gamma
• Any element that spontaneously emits radiation (shows
signs of radioactivity)
• Transmutation—changing of an atom’s nucleus such
that an new element is formed
• Alpha, beta, and proton, not neutron or gamma
• Transuranium elements-produced through induced
transmutation
Radioactive
Why does an element go
undergo transmutation?
•Before 1919, the only way to change the
nucleus, or cause transmutation, was to
wait for nature. In 1919, Rutherford was
the first to induce transmutation which
proved that nuclear reactions could be
produced artificially.
•Can occur by bombarding an atom with
alpha particles, protons, or electrons
Induced Transmutation
• Unstable
(Radioactive) nuclei
are found outside the
band of stability
• The stability of the
nucleus depends on
the neutron to proton
ratio
• If a nucleus is
unstable, it will emit
radiation (decay) to
gain stability
• Unstable nuclei (those that can be
found outside the band of stability)
losing energy by emitting radiation
in a spontaneous process
Radioactive decay
• Isotopes of atoms with unstable nuclei and go
through radioactive decay to obtain a more stable
nuclei
• Small nuclei—up to 20 protons usually stable
• Exception: Carbon—14
• Large nuclei—tend to be radioactive, based
on the ratio of neutrons to protons; ALL
nuclei with 83 protons or more are
radioactive
Radioisotope
• In a balanced nuclear equation, mass
numbers and atomic numbers are
conserved
• Alpha decay
230
90
• Electron capture
or beta capture
Th 
226
88
81
37
+ - 01 e →
Rb
Ra +
Nuclear Equations
4
2
He
81
36
Kr
Reactant  Product
Word
Bombardment
Capture
Decay
Emission (emit)
Location in the
equation
Reactant
Reactant
Product
Product
Vocab for Equations
1.
2.
97
40
218
84
Zr 
3. ? 
4.
5.
47
20
244
96
4
2
Po 
222
86
0
-1
e + ?
He + ?
Rn +
Ca 
Cm 
0
-1
4
2
4
2
He
e + ?
He + ?
Practice
Honors Only- write the equations and solve
6. Uranium-238 undergoing alpha emission
7. Krypton-81 undergoes beta capture
8. Cobalt-59 undergoes neutron bombardment,
giving an alpha decay in addition to the new
element
9. Would a)emission, b)capture, c) decay,
d)bombardment be in the reactant or the
product?
Honors Practice with words
Day 2 of Nuclear Chemistry
• Time required for ½ of a radioisotope’s nuclei to
decay into its products
• Equation: NT = N0 (1/2)n
NT =Amount remaining at time T
N0 = initial amount
n= number of half-lives
Half-life
Half-Life Formula Example 1
1. Scientists start with 50.0 g sample of a
radioisotope. How much is left after four halflives?
Honors Half-Life Formula Ex 1
1. Scientists start with 50.0 g sample of a radioisotope. How
much is left after four half-lives?
NT = N0 (1/2)n
NT =Amount remaining at time T
N0 = initial amt
n= number of half-lives
NT = (50.0 g) (1/2)4
NT = 3.125 g
NT ≈ 3.13 g
CP Half-Life Formula Ex 1
1. Scientists start with 50.0 g sample of
a radioisotope. How much is left
after four half-lives?
Half-Life Skip count
50.0 g 25.0 g 12.5 g 6.25 g 3.125 g ≈3.13 g
1
2
3
4
Half-Life Formula Example 2
2. Iron-59 is used in medicine to diagnose blood
circulation disorders. The half-life of iron-59 is
44.5 days. How much of a 2.000 mg sample
will remain after 133.5 days?
Honors Half-Life Formula Ex 2
2. Iron-59 is used in medicine to diagnose blood
circulation disorders. The half-life of iron-59 is
44.5 days. How much of a 2.000 mg sample
will remain after 133.5 days?
NT = N0 (1/2)n
NT =Amount remaining at time T
N0 = initial amt
NT =
n= number of half-lives
(2.000 g) (1/2)3
NT = 0.2500 mg
133.5 days
44.5 days
= 3 half-lives
CP Half-Life Formula Ex 2
2. Iron-59 is used in medicine to diagnose blood
circulation disorders. The half-life of iron-59 is
44.5 days. How much of a 2.000 mg sample
will remain after 133.5 days?
133.5 days
44.5 days
= 3 half-lives
 First figure out the
number of half-lives
Half-Life Skip count
2.000 mg 1.000 mg
1
0.5000 mg
2
0.2500 mg
3
• Carbon-14 is evenly
spread in Earth’s
biosphere
• Carbon-14 is
radioactive and
undergoes beta decay;
half-life of 5730 years
• Dates carbon-bearing
materials up to 62,000
years
Carbon-14 Dating
Honors-Using the graph, about what % of
carbon-14 remains after 11, 400 years?
CP- Using the graph, about how much
strontium-90 remains after 58 years?