Warm Up
10-5-15
1. Ra-225 half-life is 15 days, how many
grams are left after 45 days if you started
with 90g?
2. How can a unstable isotope (radioactive)
become normal?
3. Can radiation be good?
Agenda
Homework
-Go over quiz
-Notes Unit 3-5
-Finish WS Nuclear decay
Oct 9 - Test Unit 3
Oct 9 - Midterm Exam (45 Qs)
Oct 9 - Online HW Unit 3
Quiz Unit 3
• Version 1
1. v.e. = 5, total e = 15
2. N, Ge, In, Hg
3. Alkaline earth metals
4. Si and B
• Version 2
1. v.e. = 2, total e = 38
2. F, S, P, Ga
3. Noble gases
4. I and F
5. False, moving across the period also add
more electrons to the atom but radius decreases
6. Atomic mass and properties
Unit 3-5
Characteristics of Nuclear
Decay
Characteristics of Some Radiation
Alpha- weakest, a thin
barrier can stop (they
are big and heavy and
can’t travel very far)
Beta- clothing, wood,
or aluminum can stop
this radiation.
Gamma- highly energized
can be stop by concrete
or lead
Alpha Decay
Problem: the
nucleus has too
many protons which
cause excessive
repulsion.
Solution: In an
attempt to reduce
the repulsion, a
Helium nucleus is
emitted.
Alpha emission (decay)
4
2
He
Identify the product formed when uranium-238
alpha decays
238
92 U
4
234
He
+
Th
2
90
Determines which
atom from the
periodic table
Beta Decay
Problem: too
many neutrons not
enough protons.
Solution: a
neutron is turned
into a proton and
one electron is
then ejected.
beta emission (decay)
0
-1
e
Identify the product formed when carbon-14
emits beta particle
14
6C
0
14
e
+ 7N
-1
Gamma Decay
Problem: the
nucleus is at too
high an energy.
Solution: The
nucleus falls down to
a lower energy state
and, in the process,
emits a high energy
photon known as a
gamma ray.
gamma emission (decay)
0
0
γ
Identify the product formed when carbon-14
releases gamma rays
14
6C
0
γ
0
+
14
C
6
Explaining mass defect:
E=mc2 says that mass can
be converted into energy
when the nucleus is formed
Nuclear Fusion
- When multiple nuclei
smash into each other
forming a larger nucleus.
- How our sun produces
energy and how hydrogen
bombs work
Nuclear Fusion Equations
• Nuclear fusion involves the joining together of
nuclei.
Nuclear Fission
- A large nucleus is split into
two or more smaller nuclei
(process sped up by hitting
it with a neutron)
- Releases Alpha, Beta,
Gamma Rays and a lot of
energy
- Used to power nuclear
weapons (atomic bombs),
nuclear subs, & nuclear power
plants
Nuclear Fission
• Nuclear fission involves a nucleus breaking up into
smaller nuclei.
“Fat Man”
“Little Boy”
Nuclear Fission
Nuclear Fission
• Chernobyl power plant - 1986
Nuclear Fission
• Fukushima - 2011
Assignments
• Notes Summary
• Finish the Nuclear Decay worksheet
(due today)
Students’ Work Ethics Affected by
Peers
1. What was the main points of this news?
2. What was most important in this piece of
information?
3. How can this news be related or impact
people lives or solve problems/improve
society?
4. What is your opinion on what you heard?
Summary of Radiation
• Alpha radiation: consists of He nucleus
–
238
92
U  42 He + 23490 Th
• Beta radiation: electrons formed by the
decomposition of a neutron
–
14
6
C
0
-1
e + 147 N
• Gamma radiation: high energy
electromagnetic radiation; often emitted with
alpha or beta radiation
Summary of Radiation
Property
Alpha
radiation
Beta
radiation
Gamma
radiation
Composition
Alpha
particle (He
nucleus)
Beta particle High energy
(electron)
EM radiation
Symbol
, 42 He
, 0-1 e

Penetrating
power
low
moderate
Very high
Shielding
Paper,
clothing
Metal foil
Lead,
concrete