Transcript Radioactivity/ Twizzler Half Life Lab

Radioactivity/ Twizzler Half Life
Lab
Warm - Up
• Complete the Ions/ Isotopes WS
– PS. It is not a quiz 
Warm - Up
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State the aspects of Dalton’s atomic
theory.
Was Dalton completely correct? Why
or why not?
How is Rutherford’s atomic model
different from Thomson’s?
What are the two most accepted
models of the atom? State their
features.
Objective
• Today I will be able to:
– Explain why radioactive compounds decay
– Construct a model of half-life using Twizzler’s
– Differentiate between the composition and
materials required to shield alpha, beta, gamma,
positron and electron capture emissions
– Correctly solve and balance radioactive equations
Homework
• Radiactivity Equations Practice
Agenda
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Warm – Up
Finish History of the Atom PowerPoint
Discussion: What is radioactivity?
Half-Life Lab Investigation
Radioactive Particles Chart
Radioactivity Equations Stations
Radioactivity Review Notes
Exit Ticket
Radioactivity Notes
Class Discussion
What is Radioactivity?
What is radioactivity?
• Act of emitting radiation spontaneously
• Atomic nucleus is unstable and wants to give
up energy to form a more stable configuration
• Radiation can be given off as particles or high
energy rays
Half – Life Lab
What is a half – life for a radioactive
compound?
What is radioactivity half-life?
• Half – life – the time it takes for half of the
atoms in a given mass to disintegrate (release
radiation) and become more stable
• Length of time varies
– ½ second to a billion years
Radioactive Particles Chart
Use the textbooks in the class to find
the information on the chart and fill
in. Discuss the information with your
classmates.
Radioactivity Equations Stations
Travel to each station to get
information and solve equations for
radioactive compounds
Radioactivity Review Notes
Radioactive Decay Chains
• A nucleus goes through a series of decays and
states before it reaches a stable configuration
• Each step in the chain will have its own unique
characteristics of half-life and own type of
radiation emitted
• Understanding helps make nuclear reactors
(power) and weapons!
Uranium Chain Reaction
Types of radiation
• Transformation - Results • Results in release of
in formation of a
energy – not
nucleus of a new
transformation
element
– Gamma
– Alpha
– Beta
– Positron
Radioactive Decay – Alpha Decay
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Stream of high energy alpha particles
Consists of 2 protons and 2 neutrons
(identical to a positively charged particle of
a Helium nuclei)
An alpha particle is composed of two
protons and two neutrons, so it can be
represented by a Helium-4 atom
Radioactive Decay – Alpha Decay
• When an alpha particle breaks away from the
nucleus of a radioactive atom, it has no
electrons, so it carries a +2 charge
• An alpha particle is typically shown with no
charge, because it very rapidly picks up two
electrons and becomes a neutral helium atom,
instead of an ion
α
4
2
He
4
2
Radioactive Decay – Alpha Decay
• Heavy elements, such as
Uranium and Thorium
tend to undergo alpha
decay
• Alpha decay relieves the
nucleus of two protons
and two neutrons or a
mass of 4 amu
Radioactive Decay – Alpha Decay
• Easily stopped by clothes or paper
• Only travel several cm through air
• Usually does not pose a health risk unless
the source of radiation enters the body
Radioactive Decay – Beta Decay
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Consists of a stream of high speed electrons
A neutron breaks down into one p+ and one
eThe p+ stays in nucleus and e- leaves at high
speed
Is able to pass through clothing and damage
skin
Radioactive Decay – Beta Decay
• Example – Iodine-131, which is used in the detection and
treatment of thyroid cancer
• Notice the mass number (131) remains the same, but the
atomic number increases by one (53  54)
• This is the result of a neutron turning into a proton and an
electron – the electron leaves (as beta radiation) and the
proton remains in the nucleus
Uranium Chain Reaction
Radioactive Decay – Gamma Radiation
• Is a form of light (energy) that our eyes
don’t see
• Similar to X-rays – high energy, short
wavelength radiation
• No mass change associated with
gamma radiation
Radioactive Decay – Gamma Radiation
• Does not consist of particles
• Usually accompanies alpha and beta
radiation
• Isotopes, such as Cobalt-60 release
gamma radiation
• Very penetrating – only stopped by lead
or concrete
Radioactive Decay – Positron Emission
• Electron with a positive charge
• Formed when a proton in the nucleus decays into a
neutron and a positively charged electron – emitted
by the nucleus
• Rarely occurs with naturally occurring isotopes –
have to be man-made
Radioactive Decay – Electron Capture
• Occurs when there are too many protons and not
enough energy to release a positron
• An electron from an atom’s inner shell is taken in by
the nucleus, turning a proton into a neutron
• Energy is released – X-Ray
Radioactive Decay – Practical Uses
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PET scans
Smoke detectors
Nuclear weapons (WWII)
Source of electricity
Food preservation
Cancer treatment
Radioactive Decay – Practical Uses
• Radioactive Dating
- Uses the isotope, Carbon-14
- Produced in the atmosphere by cosmic
radiation
- A very small amount of CO2 contains C-14,
which is taken in by plants during
photosynthesis
- Animals eat plants, therefore C-14 is part
of all living things
Radioactive Decay – Practical Uses
• Radioactive Dating (continued)
- Once an organism dies, the amount of C14 begins to decrease and the half-life
(5,730 years) can be used to determine the
age
- For non-living substance, other isotopes,
such as potassium-40 are used
Exposure to Radiation
Exposure to Radiation
Exit Ticket
• Based on the poster in the classroom, what
aspects of today’s lesson relate to the
Common Core Standards?