The document discusses radioactive decay and how the nucleus changes during this process. It explains that radioactive decay occurs when an unstable parent isotope emits an alpha, beta, or gamma particle, transforming into a stable daughter product. The document provides examples of using atomic number and mass to identify daughter products from parent isotopes undergoing alpha or beta decay.

1. Launch:10/6
 Grab a your binder and immediately take a seat
 Read “Radiation Therapy” handout
 In two complete sentences describe how does
radiation therapy works? Does this help humans or
hurt humans?

2. Unit #3: Nuclear Processes

3. How does the nucleus
change during
radioactive decay?
Mr. Heffner
10/5/09

4. What is radioactive decay?
 During radioactive decay…
Parent Isotope Daughter Product
(Unstable) (Stable)
α, β, or γ particle

5. How can we predict the
daughter products?
 Three step process
 Step #1: Express isotope as a symbol
 Step #2: Set-up the equation
 Step #3: Solve and identify the element
What is the daughter product for the alpha
decay of Plutonium-240?

6. Step #1: Express isotope as
a symbol
 Plutonium-240
 Atomic mass = 240
 Atomic number = 94
Atomic mass
?
240
?
94
Pu
Atomic number

7. Step #2: Set-up the equation
240 4
94 Pu 2 He + ?

8. Step #3: Solve and identify
the element
240 4
94 Pu 2 He + ?
Atomic mass:
240 = 4 + ?
-4 -4
236 = ?

9. Step #3: Solve and identify
the element
240 4
94 Pu 2 He + ?
Atomic number:
94 = 2 + ?
-2 -2
92 = ?

10. Step #3: Solve and identify
the element
 Atomic mass = 236
 Atomic number = 92
Atomic mass
236
92
?
U
Atomic number

11. Step #3: Solve and identify
the element
240 4 236
94 Pu 2 He + 92 U

12. Exit Slip
1. Which of the following is the correct symbol for a
particle?
a. 4 He
2
b. 2 He
4
c. 0 e
-1
d. 0
0

13. Exit Slip
2. What happens to the nucleus of an atom when it
undergoes alpha decay?
a. The composition of the nucleus does not change
because it only releases energy
b. The nucleus loses two protons and transforms into a
new element due to the change in atomic number
c. The nucleus loses two neutrons and transforms into
a new element due to the change in atomic mass
d. The nucleus loses an electron and does not change
it’s identity

14. Observation: Proportion:
A Electrons in neighboring atoms neutralize
particles went straight > 98% repulsive forces between protons.
through gold foil.
B Neutrons effectively block the protons and
articles went through gold ≈ 2%
e deflected at large angles.
keep them far apart to prevent repulsion.
C Electrostatic forces between neutrons and
≈ 0.01%
Exit Slip
ticles bounced off gold foil. protons hold the nucleus together.
D Nuclear forces overcome repulsive forces
between protons in the nucleus.
information do the experimental results
reveal about the nucleus of the gold CSC20451
3. Which of the following correctly represents represents the
22 Which equation correctly the alpha
decay of polonium-214?
alpha decay of Polonium-214?
he nucleus contains less than half the mass
the atom.
he nucleus is small and is the densest part of A
e atom. 214 214 0
he nucleus contains small positive and 84 Po 85 Po +-1 e
egative particles.
he nucleus is large and occupies most of the B
om’s space.
214 2 216
CSC20056
84 Po + 4 He 90 Th
are enormous amounts of energy required
arate a nucleus into its component
ns and neutrons even though the protons C
nucleus repel each other? 214 210 4
he force of the protons repelling each other 84 Po 82 Pb + 2 He
small compared to the attraction of the
eutrons to each other.
D
he electrostatic forces acting between other
214 214 0
oms lowers the force of repulsion of the
otons. 84 Po 82 Pb + 2 He
he interactions between neutrons and CSC10110
ectrons neutralize the repulsive forces
etween the protons.

15. Exit Slip
4. The transformation of thorium-234 to
protactinium-234 is an example of
a. alpha decay.
b. beta decay.
c. gamma decay.
d. none of the above.

16. Exit Slip
5. A 2-cm thick piece of cardboard placed over a
radiation source would be most effective in
protecting against which type of radiation?
a. alpha
b. beta
c. gamma
d. X-ray

17. Homework
 Pg. 653 #1
 Pg. 657 #5a, 5b
 Pg. 670 #30, 31, 34a