Do now!
• Write 5 things that come to mind when you
hear the word “nuclear”
Nuclear Chemistry
Half-Life
Objectives
• Describe the four fundamental forces of the
atom.
• Compare and contrast nuclear fission and
fusion.
• Distinguish between alpha, beta and gamma
particles.
Essential Question
• How is energy obtained from the atom?
Another way to look at an element
What is an Isotope
• Isotope: any forms of an element that have
the same number of protons, but a different
number of neutrons.
• In other words, it will be the same element,
with a different atomic mass
Isotope examples
Half Life
• The Amount of time it takes for one-half of a
sample of atoms to decay.
Half-Life Decay of a Radioactive Isotope
Half-Life
Isotope remaining
0
1
2
3
4
5
100%
50%
25%
12.50%
6.25%
3.12%
How do they relate?
SPORTS TOURNAMENT BRACKET & HALF-LIFE
Half-Life Mini-Lab
• Let’s see half life in action
Word Problems…yay!
• 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?
Important Equations…
X = te/n
•
•
•
•
•
Y= N0(1/2)x
x = # of half-lives elapsed
te = amount of time elapsed
n = amount of time in 1 half-life
y = amount of isotope remaining
N0 = initial amount of sample
Guided Practice #1
• 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?
Steps:
1. Underline information.
2. What is the question asking?
3. Solve.
Guided Example #1
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?
1. Find out how many half-lives have gone by.
(First equation)
2. Figure out how much is left using the 2nd
equation.
Guided Practice # 2
• 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?
Independent Practice (10 min)
• Problems 7-10 on your worksheet.
• If you finish early, start working on homework.
Types of Radioactive Decay
• Alpha emission- the nucleus “spits out” a
particle that has 2 protons and two neutrons
(identical to the nucleus of helium)
• Beta emission- nucleus “spits out” a high
speed electron.
• Gamma- the nucleus “spits out” a packet of
electromagnetic radiation.
Alpha Decay
• 23892U  23490Th + 42He
Beta Decay
40
• 19K

0 e
-1
+
40 Ca
20
Gamma Decay
• 9943Tc  9943Tc + Υ
How to solve decay problems
1.
2.
3.
4.
Express the isotope as a symbol (if necessary)
Set up the equation
Identify the total mass of each individual side
The difference in masses will be the mass of
the missing element.
5. Complete steps 2 and 3 for the total protons
6. Identify the missing element
Guided Practice
1. Express the isotope as a
symbol (if necessary)
2. Set up the equation
3. Identify the total mass of each
individual side
4. The difference in masses will
be the mass of the missing
element.
5. Complete steps 2 and 3 for the
total protons
6. Identify the missing element
Guided Practice
1. Express the isotope as a
symbol (if necessary)
2. Set up the equation
3. Identify the total mass of each
individual side
4. The difference in masses will
be the mass of the missing
element.
5. Complete steps 2 and 3 for the
total protons
6. Identify the missing element
On your own…(Whiteboard)
Answers!
Independent Practice
Exit Slip
• How much of a 500 g sample of potassium-42
is left after 62 hours if the half-life of
potassium-42 is 12.4 hours?
• How many Half-lives have gone by?