Transcript The Atom and Radioactivity

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Good Afternoon!
The SLO will be administered today in Earth
Systems.
All electronic devices have to be powered off
and turned in during testing-policy
Pencils are needed
Do your best and take your time on each
question!
Assessments are used to measure learning
growth throughout the course of the year
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SLO Completion
Electronic devices turned in
Read or unit 1 vocabulary crossword for
students who are finished
Talking is not an option-no disruptions to
testing environment
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Atom – The smallest particle that has the
properties of an element.
Element – A substance that cannot be broken
down into simpler substances.
Atoms are tiny units that determine the
properties of all matter.
Atoms are made up of several different,
smaller parts.
We will focus on 3 – protons, neutrons and
electrons.
Electrons (e-) –
negative charge
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Protons (p+) –
positive charge
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Neutrons (no)–
neutral charge
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The center of the atom is
known as the nucleus.
(Orange inner circle)
The nucleus has a positive
charge.
The bulk of the mass of an
atom is in its nucleus.
It contains the protons and
the neutrons.
Outside the nucleus in
orbitals are the electrons.
The chart below summarizes the subatomic
particles in terms of location, charge and mass.
 Notice the protons and neutrons make up the bulk
of the mass of an atom.
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Particle/
Characteristic
Location in
the atom
Proton
p+
In the nucleus
Neutron
no
In the nucleus
Electron
eOutside the
nucleus in
orbitals
Charge
Mass
Positive
None
Approximately Approximately
½ mass of
½ mass of
atom
atom
Negative
Little to no
mass
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The subatomic particles determine
characteristics for elements including its
identity, mass, and charge.
The identity of an element is determined by
the number of protons in the nucleus.
Each element has a set number of protons.
The atomic number of an element is equal to
its number of protons.
This atom has a total of
3 protons.
 Because it has 3
protons, this is lithium.
 If you look at the
periodic table, you will
notice the element
with the atomic
number of 3 is lithium.
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p+ p+ p+
no no no
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The sum of the number of protons and
neutrons in the nucleus of the atom
determines its mass.
The sum is known as the mass number.
On the periodic table, the atomic mass for an
element is generally a decimal number
because it is a weighted average of all the
naturally occurring isotopes of that element.
The mass number of
this atom would be 6.
 Inside the nucleus
there are 3 protons and
3 neutrons for a total of
6.
 When you look on the
PT, you notice the
atomic mass is 6.94.
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p+ p+ p+
no no no
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Isotopes are atoms of the same element that
contain a different number of neutrons.
Since the number of neutrons is different, the
mass number will be different.
The number of protons will be the same for
isotopes because it is the identifying factor of
the element.
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These are isotopes of lithium. Notice the left
atom has a mass number of 5 and the right
atom has a mass number of 6. Both still have
3 protons which means it is lithium.
p+ p+ p+
no no
p+ p+ p+
no no no
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C-14
The symbol of the element is written
with the mass number behind it.
14
6
C
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The superscript represents the mass
number and the subscript represents the
atomic number of the element.
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Neutral atoms have no charge.
This is because they have the same number
of protons and electrons.
Since they equal, the atomic number tells you
both the number of protons and the number
of electrons for a neutral atom.
Element
Protons Neutrons
Electrons
Mass # Atomic #
Isotope
symbol
nitrogen
7
15-7=8
7
15
Nitrog
en-15
106
150
Phosphorus
Tungsten
84
7
http://app.discoveryeducation.com/search?Ntt=radioactive+decay
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Nuclei are held together by strong nuclear
forces.
These forces act over a short distance and are
between the protons and neutrons in the
nucleus of an atom.
SNF help “hold” a nucleus together.
Radioactivity is caused by an unstable
nucleus. The nucleus is unstable because the
ratio of protons to neutrons is lopsided.
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The process by which an unstable nucleus
emits one or more particles or energy in the
form of electromagnetic radiation.
The particles or energy emitted is known as
nuclear decay.
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During nuclear decay, atoms can be
transformed into isotopes or into different
elements.
We will focus on 3 types of decay.
 Alpha
 Beta
 Gamma
Definition
Symbol
Type of decay
Mass and Charge
Penetrating Power
A positively charged particle
emitted by certain radioactive
nuclei, made up of two protons and
two neutrons
α or helium isotope
Alpha
Most massive type of decay and has
a positive charge
Does not travel well through
particles because of its mass and
charge. Cannot penetrate a piece of
paper. Least harmful outside the
body, most harmful inside the body
An electron emitted by an
unstable nucleus
β or electron notation
Beta
Negative charge and little to
no mass
Travels farther than alpha
particle because of less mass.
Can penetrate paper but not a
3 mm piece of aluminum
A penetrating form of radiation
emitted by an unstable nucleus
γ
Gamma
No charge and no mass
Since there is no mass or charge,
there is nothing “slowing” it
down. Can penetrate up to 60
cm of aluminum or 7 cm of lead
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During alpha and beta decay, the number of
protons or neutrons in an unstable nucleus
changes.
For alpha decay, the nucleus emits two
protons and two neutrons.
This is the equivalent of a helium atom and is
4
represented as 2 He
For beta decay, an electron is emitted and is
represented as 0 e
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1. Evolution of the Universe Guided
2. Study Guide
3. Planet composition flipbook
4. Study of matter video notes
5. 12.3 Radioactive Dating (vocab &
questions)
6. Atom structure guided notes
7. Isotope practice worksheet
8. Warm ups (9/2-9/5)
notes
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Compare & contrast alpha and beta decay
using notes from last week.
Explain why both types of decay result in the
formation of new elements.
M&Mium Lab-bring a tear & share bag of
plain M&Ms
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We can use this information to determine the
new isotope or element formed when a
nucleus undergoes decay.
The process is very similar to a simple math
problem. It is a matter of adding or
subtracting.
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4
2
A helium atom, He is always a product in
alpha decay.
When determining the other product, you
determine the mass number by subtracting 4
from the mass number of the original
isotope.
To determine the atomic number, you
subtract 2 from the original atomic number.
Determine the symbol by looking on the PT.
226
88
Ra  He  Rn
4
2
222
86
1.
Polonium-218
2.
Radon-222
3.
Plutonium-244
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0
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An electron, e is always a product in beta
decay.
To determine the other product, you use the
same process as alpha decay.
Notice the mass number for the product is
the same as the original mass number.
The atomic number is actually one higher
than the original because you subtract a -1
from it, which is equivalent to adding +1.
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To determine the element, you would look on
the PT.
C  e N
14
6
0
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14
7
1.
Bi-214
2.
Fe-56
3.
Pb-210
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Compare & contrast alpha and beta decay-be
specific
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Radioactive isotopes will continue to go
through decay processes until the sample is
no longer radioactive.
Each radioactive isotope has a constant
decay rate known as a half-life.
Half-life – The time required for ½ of a
radioactive sample to decay.
Half-lives can last from nanoseconds to
billions of years.
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Take out a sheet of NB paper
Flatmium has a half life of 20 seconds.
Fold the paper in half during the 20 second
half life
Crumple one half of the NB paper-new
element Crumplium
Continue radioactive decay
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Describe the process of radio active decay
using your guided notes
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Explain how the Flatmium to Crumplium
model illustrates radioactive decay & half life.
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Write the following equation for the alpha
decay of Samarium-149
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Write the following equation for the beta
decay of Uranium-237
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Introduction
Mini-Chemistry Lesson
Procedures
1.Brianna P, Taylor, TJ Daniel
2. Selvin, Urias, Vanessa
3. Demi, Megan,Tamara
4. Beth, Kaitlyn, Autumn
5. Miranda, Jesse, Ana
6. Koutlas,Cody, Bryannah, Logan
7. Kenneth, Montana, Marcus
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Kyle, Luke, C.J.
Joe, Robert, Johnathan
Martin, Meghan, Chase
Emma, Shelly, Tim
Kelsey, Jailene, Toney,
Jesse, Katlyn, DaJour
Zavier, Jordan, Siera, David
Kenzey, Chris, Alex
George, Vance, Blake
Diana, Colton, Kain
LaQuandre, Nicole, Jasmine
2. Seth, Hope, Olivia
3. Simon, Trilan, Isiah
4. Emmanuel, Laura, Lester
5. Tyrel, Terry L, Erik
6. Dakota, Christopher, Tyler T
7. Dylan, Briana, Trey
8. Brianna C, Bradley, Barbara
9. Tyler D, Brandon, Emily
10. Flori, Melissa, Ivone
11. Michelle, Cierra
1.
Tell me if you are
the ONLY person
here in your group
It is OKAY to have
groups of 2 if
someone is absent.
1.
2.
3.
4.
5.
6.
7.
8.
Jessica, Branden, Sarah
Kindal, Thomas J, Christopher
Angelica, Zeke, Aaron
Lamar, Trell, Molly
Johnathen, Thomas N
Phyllicia, Krysta, Elma
Dillion, Savannah, T Padgett
Megan, Hideah, Neydy
Tell me if you are
the ONLY person
here in your group
It is OKAY to have
groups of 2 if
someone is absent.
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Think-pair-share: Explain how this activity
can be used to explain our current learning
target:
Students can explain the relationship
between radioactive decay and half life.
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Writing prompt: Students explain the
relationship between radioactive decay & half
life. (paragraph)
Refer to the Flatimum & Crumplium activity
and the M&Mium Lab to compose your
answer.
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Graph your data
Answer discussion questions (lab groups)
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Half life reflection: Explain how the M&Mium
lab helped or did not help you understand the
relationship between half-life and radioactive
decay
6.
Radioactive guided notes
Warm ups (9/8-9/12)
M&Mium Lab Handout
Half-life problems
Isotopes & decay processes
Unit 1 vocab crossword
7.
NEED PERIODIC TABLE FOR QUIZ!!
1.
2.
3.
4.
5.
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Barium-122 has a half-life of 2 minutes. A fresh
sample weighing 80 g was obtained. If it takes 10
minutes to set up an experiment using barium122, how much barium-122 will be left when the
experiment begins?
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Warm Up
Half life problems
Notes
Review of Radioactive decay
Summarizer
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Writing prompt: Describe how radioactive
decay is used to determine the age of rocks,
fossils & solar system
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All living things are made of carbon and it
exists as C-12 and C-14 (radioactive).
The ratio of C-12 to C-14 in living things is a
constant value.
As things die, the C-14 begins to decay and
the ratio changes.
When “old” things are found, scientists can
determine the ratio of C-12 to C-14 and the
“age” of the fossil can be determined.
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Keep in mind, each time a sample goes
through a half-life process, half of the sample
will remain.
In other words, after one half-life, half of the
sample will remain. After a second half-life,
¼ of the sample will remain and so on.
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1 sheet of paper
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Crossword completion (5 min)
Radiometric Dating Video Clip (8 min)
Preview of Radiometric Dating Activity
Summarizer (10 min)
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Explain how the model simulates radioactive
decay.
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Briefly explain how isotopes were used to
calculate age of the fossil.
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Radium-226 has a half-life of 1599 years.
How long would it take 7/8 of a radium-226
sample to decay?
First you have to determine how many
decays take place to get to 7/8. The first ½
life takes you to ½ the sample. Then it goes
through another decay ( ½ of ½) to ¼.
¼ of the sample then goes through a ½ life
decay to get 1/8 of the sample remaining or
in other words, 7/8 of the sample has
decayed.
 Summarizing:
1  ½  ¼  1/8
 Each arrow represents a ½ life. So the
sample went through 3 decays.
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Each decay takes 1599 years.
3 x 1599 yrs = 4797 years.
The ½ life of iodine-131 is 8.1 days. How long
will it take for ¾ of a sample of iodine-131 to
decay?
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1½¼
2 half-lives, so 2 x 8.1 = 16.2 days
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A sample of strontium-90 is found to have
decayed to 1/8 of its original amount after
87.3 years. What is the ½ life of strontium90?
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Although this is not the same problem, all we
do is work in reverse, in a way.
We figure out how many decays the sample
went through.
1  ½  ¼  1/8 3  = 3 decays
To get the length of each ½ life, take the
total decay time, 87.3 yrs., and divide by the
total number of decays.
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87.3 years ÷ 3 = 29.1 years
So each ½ life represents 29.1 years.