Science 10
Chapter 7 - Radiation
Chapter 7, Radiation and Nuclear Energy
Pg 286
7.1 Atomic Theory, Isotopes and Radioactive Decay
Radioactivity is the release of high-energy particles and rays of energy from a substance as
a result of changes in the nuclei of its atoms.
Uses – medicine, generating electricity
Radiation refers to high-energy rays and particles emitted by radioactive sources
Natural background radiation - high-energy, fast-moving particles or waves that is
found in our environment.
Electromagnetic Spectrum
-Is a name that scientists give a bunch of types of radiation when they want to talk
about them as a group. Lists the types of radiation from low frequency to high
frequency.
Wavelength
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Science 10
Chapter 7 - Radiation
Interesting tidbits of useless information brought to you by Science research...
The length of 1 wave, the higher the frequency the shorter the wavelength

A radio’s wavelength is approx. 1 m in length

A gamma ray’s wavelength is 0.000 000 000 000 001 m in length!
Electromagnetic radiation Can be described in terms of a stream of photons, which are
particles each traveling in a wave-like pattern and moving at the speed of light = 299 792
458 m / s. Each photon contains a certain amount of energy, and all electromagnetic
radiation consists of these photons.
The only difference between the various types of electromagnetic radiation is the
amount of energy found in the photons. Radio waves have photons with low energies,
microwaves have a little more energy than radio waves, infrared has still more, then visible,
ultraviolet, X-rays, and ... the most energetic of all ... gamma-rays.
Electromagnetic radiation (including visible light) travels 149 million kilometers (93
million miles) from the sun to Earth in about 8 minutes. In contrast, an automobile speeding
at 100 kilometers per hour (60 miles per hour) would require 177 years to make the same
one-way trip.
In only one second, light can circumnavigate the Earth seven times.
Useless information is now over…
_________________________________________________________
Read page 288 and summarize the work of Wilhelm Roentgen and Marie and
Pierre Curie. This is homework that will be collected for marks – keep it short –
4-5 sentences.
Isotopes and Mass Number
Pg 289
Isotopes are different atoms of a particular element that have the same number of protons
but different numbers of neutrons. All isotopes of an element have the same atomic number
(number of protons).
The mass number represents the sum of an atom’s protons and neutrons. The mass
number of an isotope is found by adding the atomic number to the number of neutrons.
Mass number = atomic number + number of neutrons
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Science 10
Chapter 7 - Radiation
Representing Isotopes
- uses standard atomic notation, which involve the symbol, atomic number, and mass
number.
The standard atomic symbols for these three isotopes of potassium (K) are
Practice pg 291 #1 - 4
Radioactive
-Any atom that emits radiation from their nuclei and forms another completely
different element
Radioactive decay is the process in which unstable nuclei lose energy by emitting radiation
Unstable radioactive atoms undergo radioactive decay until they form stable non radioactive
atoms, usually of a different element. Isotopes that are capable of radioactive decay are called
radioisotopes.
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Science 10
Chapter 7 - Radiation
Types of Radiation
Ernest Rutherford,
Three types of radiation are emitted from a nuclei - alpha, beta and gamma
Alpha Decay (α)
composed of 2 protons and 2 neutrons and have a charge of +2
-
Are helium nuclei
-
Heavy, slow moving and can be stopped by a sheet of paper
Example;
Uranium  Helium + Thorium
238
92
U
4
2
He
+
234
90
Th
Practice pg 295 #1
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Science 10
Chapter 7 - Radiation
Beta Decay (β)
- high energy electrons and have a charge of -1
- light weight, fast moving, can be stopped by a aluminum foil
Example;
Carbon  Electron and Nitrogen
14
6
0
C  1e
+
14
7 N
Carbon will lose 1 electron (e-1) therefore 6 – (-1) = 7
Practice pg 296 #1
Gamma Decay (γ)
a form of electromagnetic radiation and are not made of particles
- fast moving, little weight, can penetrate very deep into objects
- Does not give off a particle, there is no change to the nucleus
- Emits excess energy from the nucleus
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Science 10
Chapter 7 - Radiation
Summary
Property
Symbol
Alpha
Beta
Gamma
Composition
Description
Charge
Penetrating
Power
Change is mass
# of starting
nucleus
Change in
atomic # of
starting nucleus
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