Radioactivity/ Twizzler Half Life Lab

Warm - Up

• Complete the Ions/ Isotopes WS – PS. It is not a quiz 

• • • •

Warm - Up

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

• • • • • • • • 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 in formation of a nucleus of a new element – Alpha – – Beta Positron • Results in release of energy – not transformation – Gamma

Radioactive Decay – Alpha Decay • • • 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 2 4

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

• • • • Consists of a stream of high speed electrons A neutron breaks down into one p + e and one The p + stays in nucleus and e speed leaves at high 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 • • • • • • 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 CO which is taken in by plants during photosynthesis 2 contains C-14, - 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 C 14 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?