DO NOW
• Fill out the following:
• If we change the amount of protons
the mass changes
• If we change the amount of electrons
the charge changes
• If we change the amount of neutrons
the element changes
RADIATION
AIMS
• Learning objectives:
• We will learn about different types of radiation
• Success criteria:
•
•
•
•
Describe the properties of alpha, beta and gamma radiation
Recall the main sources of background radiation
Determine what types of radiation different materials can be penetrated by
Explain that radiation occurs due to unstable nuclei giving our alpha and beta
particles or gamma radiation in order to become more stable
RADIOACTIVE DECAY
• If an isotope is unstable, then it will want to turn into an isotope that is stable.
This is called radioactive decay, and the isotopes are called radioisotopes
• We already looked at what makes isotopes unstable during our investigation.
If an isotope is unstable, it is due to one of two reasons:
• It has too many neutrons
• It doesn’t have enough neutrons
• There are a few different ways we can change the number of neutrons –
ranging from getting rid of them, turning protons into neutrons, turning
neutrons into protons, and even just changing their shape
ALPHA DECAY
• Occurs via emission of an “alpha particle” (also written as α-particle, where
the first ‘α’ is actually the Greek letter alpha)
241
237
4
𝐴𝑚
→
𝑁𝑝
+
2𝛼
93
95
• The alpha particle is essentially a helium-4 isotope, and the two are used
interchangeably
• In alpha decay, the mass number will always decrease by 4, and the atomic
number will always decrease by 2
BETA DECAY
• When a neutron turns into a proton and an electron, emitting a beta (β)
particle and an antineutrino
14
14
6𝐶 → 7𝑁 + 𝛽 + 𝑣𝑒
• The beta particle is the electron made from the neutron being ejected from
the atom
• We have not covered what antineutrinos are. They’re complicated. For now,
just know that they are also emitted
GAMMA DECAY
• When the nucleus rearranges itself to become more stable, releasing a
gamma (γ) ray in the process
152
152
𝐷𝑦
→
66
66𝐷𝑦 + 𝛾
• Sometimes, you will see an “m” written in the mass number for “metastable”:
238𝑚
238
𝑈
→
92
92𝑈 + 𝛾
• Importantly, in gamma decay, no particles are released – the gamma ray is
an electromagnetic wave
CFU #1
• An alpha particle is also an example of:
1. Helium-1
2. Helium-2
3. Helium-3
4. Helium-4
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CFU #2
• In beta decay, two particles are emitted –
a neutrino and:
1.
2.
3.
4.
An electron
A proton
A neutron
A nucleus
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CFU #3
• In gamma decay, the emitted particle is:
1.
2.
3.
4.
An electron
A proton
A neutron
There is none – it’s a wave
End
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RADIATION SOURCES
• Radioactivity is actually exhibited in lots of materials
• We have a level of radioactivity (more on Thursday and hopefully Friday)
• Famously, bananas are radioactive
• We call a lot of these sources of radiation background radiation. We usually
measure the amount of harmful radiation (known as ionizing radiation) in
millisieverts (mSv).
TYPES OF BACKGROUND
RADIATION
• On average, people in the US take in about 6.24 mSv of radiation per year.
This is due to:
•
•
•
•
Cosmic radiation from space
Different foods and water (potassium in bananas, carbon-14 from metabolism)
Inhaling air (mainly from radon in the atmosphere)
Medicine (CT scans and other nuclear medicines, usually)
• There is a limit to the total amount of radiation (called the dose) the body
can survive. Calculating this dose is though is easier said than done –
different parts of the body are affected differently by radiation
RADIATION PENETRATION
• Different types of materials will let different amounts of radiation through (the
so called “penetration” of the radiation)
• The amount of radiation penetration also depends on other factors like the
thickness of the material
• The most commonly used material to protect
people from radiation is lead
CFU #4
• Which of the following is an example of
background radiation?
1.
2.
3.
4.
Food
Breathing
Space
All of the above
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CFU #5
• The harmful type of radiation is called:
1.
2.
3.
4.
Light
Waves
Electromagnetic waves
Ionizing
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RADIOACTIVITY
• Radioactivity arises when a nucleus is
unstable and wants to stabilise itself
• To stabilise itself, the nucleus will remove
particles from itself, forming entirely
different species.
• Isotopes that exhibit radioactivity are
referred to as “radioisotopes”
• These radioisotopes have plenty of
applications in our every-day lives
NUCLEAR ENERGY
• Theorised to be one of the most sustainable forms of energy. Involves the
“fusing” (fusion) of atomic nuclei to form bigger atoms, followed by the
“splitting” (fission) of atomic nuclei to form smaller atoms
NUCLEAR MEDICINE
• Involves the use of radioisotopes in the diagnosis and treatment of patients.
“Radiation therapy” as a cure to cancer has been made famous by many
TV dramas and even sitcoms
• More useful applications are in radioimaging, in which radioactivity of a
sample (called a tracer dye) in the body is measured, allowing us to create
a 3D image of a part of the patient. Most common form is PET (positron
emission topography)
RADIOCARBON DATING
• An application we will be looking into with a bit more detail next week, when
we’ve learned a little bit more about radioactivity
• Basically, all living things, and things that were once living, contain carbon,
and a certain proportion of that carbon is radioactive carbon-14
• We know how to exactly calculate how long it takes for radioisotopes to
decay
• We can combine the two to find out how old fossils are
AIMS
• Learning objectives:
• We will learn about different types of radiation
• Success criteria:
•
•
•
•
Describe the properties of alpha, beta and gamma radiation
Recall the main sources of background radiation
Determine what types of radiation different materials can be penetrated by
Explain that radiation occurs due to unstable nuclei giving our alpha and beta
particles or gamma radiation in order to become more stable
EXIT TICKET
Complete the following sentences:
1. Alpha decay results in the emission of an _______ particle (also called a ______
isotope). The isotope’s mass number will decrease by _____ and its atomic
number will decrease by _____
2. Beta decay results in the emission of a ______ particle (also called an
_________). The isotope’s mass number will decrease by _____ and its atomic
number will decrease by _____
3. Gamma decay results in the emission of a gamma ______. The isotope’s mass
number will decrease by _____ and its atomic number will decrease by _____