The spontaneous emission of energy from unstable atoms
from unstable atoms.
Atoms
natural
________ are found in all _________ matter. There are ________ atoms, which remain __________ forever, and STABLE
the same
UNSTABLE
break down
____________ atoms, which _____________ or new atoms
___________ into ____________. These unstable atoms " decay"
are said to be ________________, because they emit RADIOACTIVE
radiation
nucleus
___________ from the ________ as they decay.
Natural background radiation exists all around us.
Electromagnetic Spectrum
Electromagnetic Spectrum
energy from the Sun and other objects in the universe travels to Earth
The ________ from the Sun and other objects in the universe travels to Earth The
in ________ that we call _______________________. All of these waves electromagnetic waves
waves
travel at the speed of ______ (300, 000 km/s). Although the waves all travel light
at the same speed, they may go up and down quickly
at the same speed, they may go up and down quickly short wavelength
(__________________), while others go up and down slowly long wavelength
(_________________).
Think of these waves as if they are made up of packets of energy photons
Long
(________), with different amount of energy. ______ wavelength waves have _____ energy; ______ wavelength waves have ______ energy.
short
high
low
We call this entire range of waves of different lengths the electromagnetic spectrum .
__________________________.
Wavelength vary from several kilometres long to smaller than an atom. Wavelength
vary from several kilometres long to smaller than an atom
frequency
number
The ____________ of a wave is simply the _________ of times that the top one second
of a wave passes a point in ____________. This is called “cycles
cycles per second
second” and the scientific unit is “Hertz”
Hertz (Hz)
____________________ and the scientific unit is ________ (Hz). Waves in the Electromagnetic Spectrum
Waves in the Electromagnetic Spectrum
Wilhelm Roentgen discovered that invisible rays are emitted when he bombarded certain materials with electrons. He named it X-rays
_______ (X = unknown).
Most forms of radiation are invisible to the human eye, but they are Most
forms of radiation are invisible to the human eye but they are
present all around us all the time. One form of radiation that we can see light
is _____. Searching for the Invisible Waves
Searching for the Invisible Waves
uranium
• Henri Becquerel discovered that __________ salts emitted invisible energy. The rays emitted darkened darkened
photographic plates.
• Marie Curie and her husband Pierre named this high‐energy ray radioactivity
_____________
• The Curies also found similar results with two other elements, and named polonium
radium
d
them ___________ and _________. Review Terminologies
Review Terminologies
Mass Number
protons + neutrons
• The number of nucleons (__________________) in an atomic nucleus.
Isotopes
atomic number
• Atoms having the same ________________(protons) but different number of ____________.
b
f NEUTRONS
• Because isotopes have different numbers of neutrons, they have mass number
different ______________.
Atomic Mass
• The ______________ average of the mass numbers for all _________ of proportional
p
p
isotopes
p
an element. Standard Atomic Notation
• Example p
There are two types of boron atoms:
‐ 19.9% of boron atoms have 5 neutrons
19.9% of boron atoms have 5 neutrons
‐ 80.1% of boron atoms have 6 neutrons
To find the atomic mass of boron:
10
Atomic number 5 B
Mass number
Mass number
10 x 19.9%
10 x 19.9%
+
11
5 B
+
11 x 80.1%
11 x 80.1%
= 10.8
10
5B
11
B
5
• Example There are three types of potassium isotopes:
‐ 93.2% of potassium‐39
‐ 1.0% of potassium‐40
‐ 6.7% of potassium‐41
To find the atomic mass of potassium:
39
K
19
39 x 93.2%
+
40
K
19
+
41
K
19
+
40 x 1.0%
+
41 x 6.7%
= 39.1
39.1
39
K
19
40
K
19
41 K
19
Radiation
high-energy
y y
• The release of _____________ rays and particles given off by radioactive _____________
p
g
y
sources
DECAY
((Unstable nucleus))
(radiation)
Small fast-moving
Small,
fast moving particles
(invisible)
The level of radioactivity depends on how stability the atom is
atom is
Ion or new atom
(Stable or relatively more stable)
• When atoms lose high energy particles and waves, _____ or even ions
new atoms
___________ can be formed.
Radioactive Decay
Radioactive Decay
radioisotopes
Some isotopes are radioactive, and they are called ______________.
Radioisotope uranium-238 decays in several stages until it finally becomes lead-206
alpha
beta
There are three types of radiation: _______ particles, _____ particles, and _________ particles.
gamma particles
lead
Ernest Rutherford placed a radioactive source inside a _____ block that allowed the radiation to pass out only through a tiny hole. From the hole, the radiation travelled through a slot between electrically charged
the radiation travelled through a slot between ____________________ plates that deflected any electrically charged particles.
positively charged
Alpha: the ____________________ particles that were deflected toward the negative plate
toward the negative plate. negatively charged
Beta: the ____________________ particles that were deflected toward the positive plate. Gamma: the _________ particles that passed right through the neutral
electric field unaffected.
Alpha Radiation
Alpha Radiation
Alpha radiation is a stream of _______________, ___.
Alpha
radiation is a stream of alpha particles α
Positively charged
massive
• __________________, and are the most _________ of the radiation types.
two neutrons ___ charge
+2
two protons
• It has ____________ and _____________ Æ
4
2
α or He
4
2
alpha decay
• Release of alpha particles is called _____________ less
slow
• Alpha particles are _____ and penetrate materials much ____ than sheet of paper
the other forms of radiation. A ______________ will stop an alpha particle
particle.
• Example
Alpha decay
Radium-226 releases an alpha particle and becomes
Radon-222. Radon has two less protons than radium.
Beta Radiation
Beta Radiation
Beta radiation is an ________, ___ .
Beta
radiation is an electron β
Negatively
zero
tiny
• ___________ charged (‐1), very _____, and mass of _____.
electron
neutron
• Occurs when a ________ changes into a _______ and an ________. proton
released
‐ The proton _____ in the nucleus, and the electron is _________. stays
ee of aluminum foil to stop a beta particle.
• It takes a ___________________________ to stop a beta particle.
It takes a thin ssheet
0
-1
β or e
0
-1
• Example
Beta decay
Iodine-131 releases a beta particle and becomes Xenon-131.
A neutron has turned into a proton + the released electron
electron.
131
53
I →
131
53
I →
131
54
Xe +
or
131
54
Xe +
0
–1
β
0
–1
e
Gamma Radiation
Gamma Radiation
γ
high energy short-wavelength
Gamma radiation is a ray of _____________, __________________ radiation, ___ .
γ
0
0
no mass
• Has __________ and _________
no charge
highest energy
• Is the ________________ form of electromagnetic radiation.
thick blocks of lead
concrete
• Takes ____________________ or _________ to stop gamma rays
• Gamma decay results from energy being released from a high‐
energy nucleus
• Example
60
28
Ni* →
Ni
60
28
Ni + γ
0
0
Gamma radiation can also be released by other kinds of radioactive decay.
• Example: Uranium‐238 decays into an alpha particle and also releases gamma rays
238
92
U →
234
90
Th + 42 He + 2γ
Nuclear Equations
Nuclear Equations
Nuclear equations are written like chemical equations, but represent q
q
,
p
changes in the nucleus of atoms.
• Chemical equations represent changes in the position of atoms, not changes to the atoms themselves.
h
h
h
l
1. The sum of the mass numbers should equal.
2. The sum of the charges should equal.
• Examples
238
92
U →
234
90
Th + He + 2γ
4
2
Homework
1 Textbook pg 301 #1 13
1. Textbook, pg. 301 #1‐13
Radioactivity Review
Radioactivity Review
http://www.youtube.com/watch?v uJzSpzrEo0k&feature related
http://www.youtube.com/watch?v=uJzSpzrEo0k&feature=related
ages
Radioactivity can be used to help determine the ______ of objects by relative
radioactive
measuring the _________ amounts of remaining ____________ material to stable p
_______ products formed.
_______
Example:
Carbon dating
g measures the ratio of ___________
carbon-12 (stable) _______________
(
)
carbon-14
and __________ (radioactive).
Carbon Dating
Carbon Dating
In nature, C
In
nature, C‐12
12 and C
and C‐14
14 exists in a __________ exists in a constant
ratio. C‐12 appears 98.9% of the time whereas C‐
14 atom only appears for every 1 trillion normal atoms.
stops
When organisms die, C‐14 ______ being created radioactive decay
and slowly undergo ___________________. By measuring the relative amounts of C‐12:C‐14, we i th
l ti
t f C 12 C 14
can determine the age of the organism. This is called ___________________.
radiocarbon dating
Radiocarbon dating only works for organisms less than 50, 000 years old. The half‐life of C‐14 is 5730 years
___________.
Half life
Half‐life
Half-life
Half
life : the time required for half of the radioactive sample to
__________: the ______ required for _____ of the radioactive sample to decay. For a radioactive element, the half‐life is a constant rate of decay.
Example:
Half‐life of C‐14 is 5730 years. This means that if you have 10g of C‐14 today, there will be 5g remaining in 5730 years.
today, there will be ____ remaining in 5730 years.
Example:
Half‐life of Strontium‐90 is 29 years. How many half‐lives have passed when there is 25% of the original amount of Strontium‐90 remaining?
2 half lives (58 years)
Example:
Iodine‐131 is an isotope used in the treatment of thyroid cancer. Iodine‐
131 has a half‐life of 8 days. If a sample of iodine‐131 weights 20g, what mass of iodine would remain after 16 days?
y
Example:
A sample of rock contains 64g of a radioisotope. How much of the radioisotope will remain after three half‐lives?
Decay Curve
Decay Curve
Decay curves
rate
______________ show the ______ of decay for radioactive elements. They half-life
also show the relationship between _________ and ____________ of percentage
original substance remaining.
Besides C‐14, there are many radioisotopes that can be used for dating.
Parent
________ isotope = original, radioactive material
Daughter
___________ isotope = stable product of radioactive decay
The rate of decay remains constant, but some elements require one step to decay while others decay over many steps before reaching a stable daughter isotope.
isotope
Example:
one step
t
C‐14 decays into N‐14 in _________.
Example:
multi-steps
U‐238 decays into Pb‐206 in ____________!
y
____________
Potassium‐40
Potassium
40 Clock
Clock
Radioisotopes with very long half‐lives, such as the potassium-40/argon-40 clock
______________________________ (half‐life: 1.3 billion yrs), can help very old
determine the age of _________ things.
Example:
p
The K‐40 clock can be used to determine the age of Earth. rock is produced from lava all the gases in the molten
When ______ is produced from lava, all the gases in the molten When
driven out
rock, including argon‐40, have been ___________. This process sets the potassium radioisotope clock to zero, because there is potassium‐40
potassium
40 (parent) present in the molten rock, but no argon
(parent) present in the molten rock, but no argon‐40
40 (daughter) present.
cools
As the molten rock ______ over time, K‐40 decays to Ar‐40 and gets trapped within the rock. By measuring the ratio of K‐40:Ar‐40, it age
will be able to help us determine the _____ of the rock.
Brainiac (Cooking an Egg with 200 mobile phones)
http://www.youtube.com/watch?v=Rc-ne-nIKUY
Brainiac (Microwaves-Newton's Cradle)
http://www.youtube.com/watch?v=Lkn6fMn9eqU
What is a Nuclear Bomb?
http://www.youtube.com/watch?v=vGkOFEpnfIs&feature=related
Homework
1 T tb k
1. Textbook, pg. 311 #1‐13
311 #1 13
Chemical Reactions
conserved
• Mass is ____________
Energy changes
• _______________ are relatively _______
small
nuclei
• No changes to the _______
Nuclear Reactions
Nuclear Reactions
change
Reactions that involve a ________ in an atom’s nucleus
________, such as gaining or releasing particles, or ________,
g
g
gp
,
energy.
Examples:
p
fission
fusion
Nuclear _______ and Nuclear _______
Nuclear reactions can release subatomic particles N
l
i
l
b
i
i l
protons neutrons electrons
(________, _________, _________, or all three) as gamma rays
well as ______________.
One of the characteristics of nuclear reactions is small
mass
that a _______ change in _______ results in a l
large
energy
________ change in _______.
chemical
Difference between __________ reactions and ________ reactions:
nuclear
Nuclear Fission
Nuclear Fission
Fission : _________
Splitting
p
heavy
y (unstable) nucleus into two or more ________
of a ________
(
)
________ nuclei, as well as some sub‐atomic particles and ________.
smaller
energy
Heavy nucleus is usually _________ because it has too many protons unstable
(positively charged particles) pushing apart.
Produces neutrons and extremely large amount of energy (it can generate enough __________ electricity
to support our lifestyle).
Example:
Ontario, Quebec, and New Brunswick are currently using
Brunswick are currently using nuclear power
CANDU
Canadian‐made nuclear reactors are called ________ reactors (stands for Canadian deuterium uranium). These are used in Canada, South Korea, Chi
China, India, Argentina, Romania, Pakistan, etc.
I di A
ti
R
i P ki t
t
These reactors are known to be safe and easy to shut down in an emergency. Heat energy produced turns electricity‐generating turbines.
The energy (heat) produced from the nuclear reactions is used to boil water turbines
g
_______,
__________
p
and generate _______, which then drives the __________ that produce steam
electricity. A turbine is a large rotating device that can be forced to turn when steam is applied to it.
Even though these nuclear reactions can ________ the need for reduce
burning fuels
______________, such as coal and natural gas, and can generate large enough h
l d t l
d
t l
h
amount of energy to generate power to support our lifestyle, a number of hazards
potential _________ and problems exist with the use of nuclear reactors.
Examples:
• Hazardous wastes
‐ Takes 20 half‐lives before material is safe store safely
‐ How to ____________ for hundreds of thousands of years? Deterioration
• _______________ of the nuclear power plants
nuclear weapons
• Materials can be used for making __________________
Induced Nuclear Fission
Induced Nuclear Fission
induce
Besides the natural radioactive decay, scientists can also force (________) nuclear reactions to occur.
Example:
Induce a nuclear reaction by bombarding a nucleus with alpha, beta, or gamma radiation.
α+
14
7
He +
14
7
4
2
4
2
N →
or
17
8
N →
17
8
O + 11 p
O + 11 H
Review: Writing Nuclear Equations
Review: Writing Nuclear Equations
Rules for writing these equations are the same as earlier nuclear equations:
Mass numbers
• _______________ must equal on both sides of the equation
Charges must equal on both sides of the equation
• _________ must equal on both sides of the equation
Textbook, pg. 3 5 # 5
Textbook, pg. 315 #1‐5
Recall:
It actually takes a tremendous amount of energy for an _______ alpha
particle (+2 charge) to collide with a N‐14 nuclear (7 protons, +7 charge) i l (
h
)
llid i h
l
(
h
)
because the __________ between the positive charges is quite big.
repulsion
It is much easier to crash a neutral __________ into a nucleus instead of It
is much easier to crash a neutral neutron into a nucleus instead of
a positive proton to release energy!
Example:
N l
Nuclear fission of Uranium‐235
fi i
fU i
235
The induced nuclear fission of
uranium-235. This nuclear
reaction is the origin of nuclear
power and nuclear bombs.
Induced Nuclear Reaction
Radioactive Decay
Summary:
Chain Reactions
Chain Reactions
Chain Reaction
________________: the process in which one reaction initiates the next keep
pg
going
g.
reaction, and it can ,
____________
Induced Reaction
neutrons
The __________ released in the induced reaction can ________ more trigger
reactions on other U‐235 atoms. As you can imagine, this chain reaction can quickly get out of control ! Uncontrolled chain reactions can result in the
quickly get ______________! Uncontrolled chain reactions can result in the nuclear bombs
release of excess energy of harmful radiation Æ creation of ______________!
One possible way to control this chain reaction is to ________ some of the O
ibl
t
t l thi h i
ti i t absorb
f th
_________ that are being produced to ensure that the reaction stays at safe neutrons
levels.
Nuclear Fusion
Nuclear Fusion
Nuclear Fusion : joining of two light
_______________: joining of two _______ nuclei into one heavier
_________ nucleus.
Example:
Two isotopes of hydrogen nuclei join heat
under tremendous ______ and pressure
_________ to form a helium nucleus at Sun
the core of the _____ and other stars. energy
Huge amount of _______ are released when helium atom is formed.
The energy that is generated passes from the Sun as radiation and brings ______ and ______ to our world.
heat
light
It is difficult to harness the energy of nuclear fusion because we have yet to find a safe and manageable method to do so.
Obstacles:
high
‐ Need to achieve the ______ temperatures and pressure needed for nuclear fusion to occur.
vessel
‐ Find a way to contain a reaction that is so hot that no ________ can hold it without being destroyed.
Homework
1 T tb k
1. Textbook, pg. 325 #1‐11
325 #1 11
2. Ch. 7 Test (Jan 14)
‐ Review: Textbook, pg. 326‐327 #1 30
#1‐30