Transcript PS Unit 10 Nuclear Reactions
Nuclear Reactions
Chapter 10
Standards
• • • • •
SPS3
. Students will distinguish the characteristics and components of
radioactivity SPS3a
. Differentiate among
alpha particles and gamma radiation.
and
beta SPS3b
. Differentiate between
fission fusion
.
SPS3c
. Explain the process radioactive decay.
half-life
and as related to
SPS3d
. Describe
nuclear energy
, its practical application as an
alternative energy source
, and its
potential problems.
Nuclear Radiation
Radioactive Decay : unstable isotopes emit particles and release energy to become stable
•
isotopes.
after radioactive decay, the element changes into a different isotope of the same element
or into an entirely different element.
Radiation
Nuclear Radiation
: particles and energy
released from the nucleus during radioactive decay.
Types of Radiation
•
Alpha (
)
-protons and neutrons
2 4 He 2+
paper •
Beta-minus (
-)
-electrons and positrons
0 -1 e
•
Gamma (
)
high-energy photons
1-
lead
0
concrete
Types of Nuclear Radiation (pg 238)
Radiation Type Symbol
Alpha particle Beta particle Gamma ray
What is it? Mass (kg)
2 protons and 2 neutrons 6.646x10-27 Fast-moving electrons or positrons 9.109x10-31 Form of electromagnetic energy None Charge +2 -1, (+1) 0 Travel depth through materials Least far due to massive size Farther than alpha, but still not far Through clothes; Can cause harm Neutron A neutron leaving the nucleus 1.675x10-27 0 Penetrate the farthest
Nuclear Decay
• • • • Anytime an unstable nucleus emits alpha or beta particles, the number of protons and
neutrons changes.
Alpha decay
: atomic mass and number
change Beta decay
: atomic number changes
Gamma decay
: energy of the nucleus is lower, but no change in atomic number or mass
Nuclear Decay
•
Why nuclide (nucleus of an isotope) decay…
to obtain a stable ratio of neutrons to protons 39
K
19 40
K
19 Stable Unstable (radioactive)
Alpha Decay
226 88 Ra 222 86 Rn + 4 2 He
226 = 222 + 4 88 = 86 + 2
(atomic mass & atomic number change)
Beta Decay Equations
14 6
C
14 7
C +
0 -1
e
14 = 14 + 0 6 = 7 + (-1)
( atomic mass stays the same; atomic number changes by 1)
Actinium-217 decays by releasing an alpha particle. Write the equation for this decay process and determine which element is formed.
227 89
Ac
A Z
X +
4 2
He
Complete the following radioactive-decay equation. Identify the isotope X. Indicate whether alpha or beta decay takes place.
63 28
Ni
A Z
X +
0 -1
e
Radioactive Decay Rates
•
Half-life
: time in which half of a radioactive substance decays; measure of how quickly a substance decays.
-Iodine-131: used by doctors to diagnose medical problems -Potassium-40: used by geologists to predict the age of rocks
Calculating Half-Life
• Radium-226 has a half-life of 1599 years. How long will 7/8 of a sample take to decay?
1. Find out how much will be left. 8/8 - 7/8 = 1/8 left over 2 .
Calculate how many half-lives until only 1/8 is left.
One half life Two half lives Three half lives 1
1/2 1/4 1/8
3. Calculate how many years it will take for 3 half lives
to occur.
1599 x 3 = 4797 years
Nuclear Fission
•
Nuclear fission
: the process by which a
nucleus splits and neutrons and energy are released.
•
Nuclear chain reaction
: a continuous series of fission reactions (pg 340)
Nuclear Fusion
•
Nuclear fusion
: when 2 light nuclei combine
to form a heavier nuclei
-Hydrogen is turned into Helium on the sun.
(pg 342)
Radiation on Earth
• • All around you.
Background radiation
: arises naturally from the sun, soil, rocks, and plants • You are exposed to more radiation in the mountains than at sea level
Beneficial Uses of Radiation
• • • • Smoke detectors release alpha particles Radiation is used in x rays, MRIs, CT scans, PET scans, and ultrasounds Radiation therapy is used to treat cancer Used in agriculture to track the flow of water
Nuclear Radiation Risks
• • High levels of radiation exposure can cause radiation sickness High concentrations of radon gas can cause cancer
Nuclear Power
Advantages Disadvantages Does not produce greenhouse gases Radioactive products must be handled and stored carefully so they do not escape.
Much more energy available in uranium reserves than gas and coal.
Expensive to build due to many safety regulations.
Waste must be stored in areas away from people, homes, water, earthquakes .