DO NOW
When the bell rings
• In your seat:
• With pen/pencil
• With Notebook
• With Handouts
• Silent and ready for
Do Now
• Homework on your
desk
After the bell (2 min)
Respond to the
following:
“Don’t watch the
clock; do what it
does. Keep going.”
-Sam Levenson
NUCLEAR CHEMISTRY:
HALF-LIFE
Objective:
Describe the decay of isotopes through half-life
AGENDA
HONORS/
PRE-IB
 Do Now (5 min)

Upcoming: Unit 2 Test
Warm Up (5 min)
Notes: Half - Life(30 min)
 Activity: Half-Life of a penny
(10 min)
Independent Practice: (20
min)
 Exit Slip (5 min)
Closeout (2 min)
GUIDING QUESTION
• Why can’t you just clean up after a
nuclear disaster?
WARM –UP:
How?
• C – Level 1-2,
amongst group
• H – Raise hand
• A – Discuss prompt
• M – None
• P –Recording
responses on left
page, discussing with
group
What?
• Draw the Bohr model for
Neon
• An ion occurs when an
atom gains or loses
electrons to form a bond.
Draw the Bohr model for
an atom of Cl that gains
an electron when it
bonds with Na.
• What is the resulting
charge?
• What is an isotope?
• Isotope: any forms of an element
that have the same number of
protons, but a different number of
neutrons.
ISOTOPE
• In other words, it will be the same
element, with a different atomic
mass
ISOTOPE
EXAMPLES
HALF - LIFE
Definition: The
Amount of time it
takes for one-half
of a sample of
atoms to decay.
Half-Life Decay of a
Radioactive Isotope
Isotope
Half-Life
remaining
0
100%
1
50%
2
25%
3
12.50%
4
6.25%
5
3.12%
March Madness Bracket
LOOKS LIKE
THIS…
HOW MUCH
WILL REMAIN
1. Set up a 3 column
table
2. Label the columns:
half-life, time, amount
3. Fill in the information
you are given (starting
with time 0 and halflife 0, for original
amount only)
4. Work forwards or
backwards to reach
the answer
• Barium-122 has a half-life of 2
minutes. If you receive 80 g of
Barium-122, how much will be
remaining after 10 minutes?
Half-Life
Time
Amount
YOU DO
1. Set up a 3 column
table
2. Label the columns:
half-life, time, amount
3. Fill in the information
you are given (starting
with time 0 and halflife 0, for original
amount only)
4. Work forwards or
backwards to reach
the answer
• How much of a 100.0 g sample
of 198Au is left after 8.1days, if
its half-life is 2.70 days?
HOW MUCH
TO BEGIN
WITH
1. Set up a 3 column
table
2. Label the columns:
half-life, time, amount
3. Fill in the information
you are given (starting
with time 0 and halflife 0, for original
amount only)
4. Work forwards or
backwards to reach
the answer
• There are 5 g of 131I left after 40.35
days. How many grams were in the
original sample if its half-life is 8.07
days?
Half-Life
Time
Amount
?
40.35 days
5g
YOU DO
1. Set up a 3 column
table
2. Label the columns:
half-life, time, amount
3. Fill in the information
you are given (starting
with time 0 and halflife 0, for original
amount only)
4. Work forwards or
backwards to reach
the answer
• If the passing of five half-lives
leaves 25.0 mg of a strontium-90
sample, how much strontium-90
was originally present?
Half-Life
Time
Amount
LENGTH OF
HALF - LIFE
Total time
elapsed
Number
of half
lives gone
by
Length
of a
single
Half-Life
• If 100g of Au-198 decays to 6.25 g
in 10.8 days, what is the half-life of
Au-198?
Half-Life
Time
Amount
0
0
100g
1
?
50
2
?
25
3
?
12.5
4
10.8 days
6.25g
• A 50.0 g sample of 16N decays to
12.5 g in 14.4 seconds. How long is
its half-life?
YOU DO
Half-Life
Total time
elapsed
Number
of half
lives gone
by
Length
of a
single
Half-Life
Time
Amount
MINI – LAB: HALF-LIFE
How?
• C – Level 1-2, on-task
discussion
• H – Raise hand
• A – Answering questions as a
small group at lab
• M – None
• P – Recoding answers on
worksheet, head up, reading
and thinking through all
questions, discussing with
group
What?
• Instructions are in
your packet
• Using 50 coins, not
100
• Using Tupperware
instead of Ziploc
bags
ACTIVITY: INDEPENDENT PRACTICE
How?
• C – None
• H – Raise hand
• A – Answering questions
to determine # of
subatomic particles
• M – None
• P – Recoding answers
on worksheet, head up,
reading and thinking
through all questions.
What?
• 10 minutes silently 
Discuss for 5 minutes
in small groups 
Verify & Review as
class
EXIT SLIP
How?
• C – No talking
• H – Raise hand
• A – Taking exit
slip
• M – In seat
• P – Completing
exit slip without
notes and
turning in
What? (5 min)
• If you finish early,
summarize what you
learned at the bottom
of your notes OR
answer today’s guiding
question
Forgetting to
stretch is a
bear.
CLOSING
• What are 3 key takeaways
from today and yesterday?
• Complete the 3 stretch
questions
• Be ready to discuss Fusion,
Fission and Decay next class