Download Nuclear Chemistry PP1

Isotope: same element (same #P) different
number of neutrons (different mass #)
Carbon-12 has 6 protons and 6 neutrons
Carbon -14 has 6 protons and 8 neutrons
Therefore, C-12 and C-14 are isotopes
Element Name

Carbon-14

C-14
Atomic Mass
Symbol
Atomic Number

When the size and mass of the nucleus becomes large (greater
than atomic #83), the element is known to be radioactive
(unstable) because it decays.
 Examples:
▪ Pu-239 (94 protons)
▪ U-238 (92 protons)

When the ratio of neutrons to protons is greater than 1:1 (for
light nuclei) , the element is also radioactive.
 Examples:
▪ Carbon-14
▪ Lithium-7

Different than mass #

Weighted average of all naturally occurring
isotopes of an element
Weighted Average: You have to take into
account the amount of each isotope present
in a sample
1.
2.
3.
Convert % to a decimal.
Multiply the mass by the decimal.
All products are added together.
If 75.0% of the isotopes of an element have a
mass of 35.0 amu and 25% of the isotopes
have a mass of 37.0 amu, what is the atomic
mass of the element?
0.75 x 35 = 26.25amu
0.25 x 37 = + 9.25 amu
35.5 amu
Does this answer make sense?
 Radioactive atoms emit radiation because their
nuclei are unstable*.
 Unstable nuclei lose energy by emitting radiation
in a spontaneous process called radioactive
decay.
 Radioactive decay continues until stable,
non-radioactive atoms form. They are often of a
different element.


Occurs when nuclei are unstable.
For any element, an isotope that is unstable is
called a radioisotope.



Unstable nucleus emits an alpha particle (α,
)
Decreases the mass number by 4 and the
atomic # by 2
Associated with heavy nuclei (above 83)



Unstable nucleus emits a beta particle (β-, )
 Turns a neutron into a proton
▪ Decreases N:P ratio
Favorable when the N:P ratio is high (above 1.0)
Found above the band of stability
An unstable nucleus emits a positron (β+,
)
 Proton turns into a neutron
 Favorable when the N:P ratio is low(below
 1.0)
 N:P increases
 Isotopes found below the band of stability


Begins with one nucleus that spontaneously
decays.
***Always has ONE REACTANT.


The atomic mass one side of the arrow has to
equal the mass on the other side of the arrow
The atomic number one side of the arrow has
to equal the atomic number on the other side
of the arrow
Nuclear involve the nucleus of atoms.
Radioactive elements have unstable nuclei.
Unstable nuclei will release particles until a
stable nuclei results
Which particle is the most
massive (has the largest
mass)?
alpha
Which particle has no mass?
gamma (type of
electromagnetic
radiation)

When a nucleus decays, it emits particles.
Particle
Mass
Charge
Symbol
Penetrating
Power
Alpha
4 amu
2+
,
Low
Beta
0 amu
1-
-,
Positron
0 amu
1+
Gamma
0 amu
none
2
4He
-1
0e
+ 10e
,
0
0 
Moderate
Moderate
High
Natural Transmutation: occurs spontaneously
releasing either:
Alpha particle
Beta particle
Positron particle
Gamma radiation
Alpha Decay
252 Md
227 Ac
221 Fr
207 At
4
2
He
181 Ir
Beta Decay
6
3
Li
24
12
Mg
201
80 Hg
52
27 Co
0
-1
β-
42
20
Ca
Positron Decay
75
34
Se
30
14 Si
27
13 Al
45
21 Sc
0
+1
β+
8
4
Be
Which particle is emitted when an atom of Kr-85 spontaneously decays?
Which particle is emitted when an atom of Kr-85 spontaneously decays?
Beta (β-)
Which list of radioisotopes contains an alpha emitter, a beta
emitter, and a positron emitter?
(1) C-14, N-16, P-32
(2) Cs-137, Fr-220, Tc-99
(3) Kr-85, Ne-19, Rn-222
(4) Pu-239, Th-232, U-238
What is the half-life and decay mode of Rn-222?
(1) 1.91 days and alpha decay
(2) 1.91 days and beta decay
(3) 3.82 days and alpha decay
(4) 3.82 days and beta decay
Artificial Transmutation: forcing decay
by bombarding a nuclei with a high
energy particle

Radioactive Dating:
 Carbon-14 (once living things)
 U-238 (rocks)

Tracing Chemical and Biological Processes
 Radioactive tracers are injected into the body and then x-
rayed
▪ Radioactive substance shows up on the X-ray

Detecting and Treating Disease
 Sr-90:diagnosing and treating bone cancer
 I-131: diagnosing and treating thyroid disorders
 Co-60, Tc-99:cancer treatment

Kill Bacteria in Foods