section 18.1 radioactivity 1.define radiocarbon dating and list three items that have been...

Section 18.1

Radioactivity

1. Define Radiocarbon Dating and list three items that have been radiocarbon dated and the significant findings of the results.

2. Describe, define, draw the 3 water cycles of a nuclear power generation facility.

3. Describe 3 safety control procedures to help prevent a nuclear meltdown.

4. Detail the 3 major nuclear reactor “incidents”.

5. List the options for short term and long term storage or disposal of spent nuclear fuel rods.

Objectives

Section 18.1

Radioactivity

1. To learn the types of radioactive decay

2. To learn to write nuclear equations for radioactive decay

3. To learn how one element may be changed to another by particle bombardment

4. To learn about radiation detection instruments

5. To understand half-life

Objectives

Section 18.1

Radioactivity

• nucleons – particles found in the nucleus of an atom

– protons

– neutrons

• atomic number (Z) – number of protons in the nucleus

• mass number (A) – sum of the number of protons and neutrons

A Review of Atomic Terms

Section 18.1

Radioactivity

• isotopes – atoms with identical atomic numbers but different mass numbers

• In other words, the same number of protons, different # of neutrons

• nuclide – a general term for each unique atom

• Parent-daughter nuclides -

A Review of Atomic Terms

Section 18.1

Radioactivity

A. Radioactive Decay

• Radiation – general term for energy

• radioactive – nucleus which spontaneously decomposes forming a different nucleus and producing one or more particles

• nuclear equation – shows the radioactive decomposition of an element

Section 18.1

Radioactivity

• Alpha Particle – helium nucleus 42He

• Beta negative Particle – electron 0-1e

• Beta positive Particle 01e

• Gamma Ray – high energy photon – nucleus does not change mass # or atomic #

• A ???? + B .

• Electron Capture**A + 0-1e B 0

Types of Radioactive Decay

Section 18.1

Radioactivity

• Why do these parent nuclides decay?

• The daughter nuclides are more stable-

Radioactive Decay

Section 18.1

Radioactivity

Ionizing Radiation has the potential of altering DNA…

Blinky

Real or not?

Who lives in a pineapple under the sea?

Section 18.1

Radioactivity

Section 18.1

Radioactivity

• Alpha-particle production

• Alpha particle – helium nucleus 42He

– Examples

• Net effect is loss of 4 in mass number and loss of 2 in atomic number.

Section 18.1

Radioactivity

– Write the Nuclear Decay Reaction of Ra-226 by alpha emission… 4

– 22688 Ra + 4

– What would happen if Rn underwent alpha decay?

– 22286 Rn

Section 18.1

Radioactivity

• Write the Alpha Decay Equation for:

• Po-210

• 21084 Po

• 23892 U

• 23090 Th

• 21884 Po

• 21484 Po

• Nature of Stability is due to proton arrangement• Stability predictions related to Mass # and Molar Mass

Section 18.1

Radioactivity

• Beta negative-particle production

• Where does the e- come from??

• Net effect is to change a neutron to a proton because a neutron is made up of a proton and electron…

• 10n 1

+1p + 0-1e

• Beta particle – electron 0-1e

– Examples

Section 18.1

Radioactivity

• Beta neg particle – electron 0-1e

• Write the beta decay equation for:

• 22789 Ac + 0

• 146 C

• 22789 Ac

Section 18.1

Radioactivity

• Beta Positive particle (positron) 01e

• Net effect is to change a proton to a neutron.• Think of the proton as being a neutron

(proton and e-) with an extra positron

• Positron – particle with same mass as an electron but with a positive charge

Section 18.1

Radioactivity

• Positron production 01e

• Write the Positron Production equation for:

• 137 N + 0

• 3819 K

• 158 O

Section 18.1

Radioactivity

• Gamma ray release

• Net effect is no change in mass number or atomic number.

• A A + energy

• Lower energy, more stable

• Gamma ray – high energy photon (energy)00

Section 18.1

Radioactivity

• Electron capture 0-1e

– Explain this on a subatomic (nucleon) level…

Section 18.1

Radioactivity

– When a nucleus grabs an inner orbital e- transforming a proton to a neutron

– What else is happening in this example?

Section 18.1

Radioactivity

• Write the e- capture equation for:

• 7333 As + 0

• 4019 K

• 13757 La

Section 18.1

Radioactivity

Section 18.1

Radioactivity

Decay series and Nuclear Particles Video

Section 18.1

Radioactivity

• Tell what kind of decay these undertake:

• 11647 Ag + 116

• 21183 Bi + 207

• 158 O + 15

• 21089 Ac + 206

• 13153 I + 131

• 8835 Br + 88

Section 18.1

Radioactivity

• Write the decay equation for:

• 22688 Ra by alpha

• 21482 Pb by beta

• 116 C by positron

• 19579 Au by e- capture

Section 18.1

Radioactivity

B. Nuclear Transformations

• Nuclear transformation – change of one element to another

• Bombard elements with particles (reverse of decay…)

Section 18.1

Radioactivity

B. Nuclear Transformations • Transuranium elements – elements with atomic numbers

greater than 92 which have been synthesized

Section 18.1

Radioactivity C. Detection of Radioactivity and the Concept of Half- life • Geiger-Muller counter – instrument which measures

radioactive decay by registering the ions and electrons produced as a radioactive particle passes through a gas-filled chamber VIDEO

Section 18.1

Radioactivity C. Detection of Radioactivity and the Concept of Half- life • Half-life – time

required for half of the original sample of radioactive nuclides to decay VIDEOS

• Will the original quantity ever be depleted?

Section 18.1

Radioactivity

C. The Concept of Half- Life

• Given the half life of Pa-234 is 1.2 minutes, what fraction of the original sample will remain after 7.2 minutes?

• 6 half-lives

• 1.56%

• How many half lives need to pass until the original amount is essentially depleted?

• 12? 14? 16?

• How much time would it take to pass 16 ½ lives?

Section 18.1

Radioactivity

• Given the half life of U-238 is 4.5 X 109 years (4.5 billion), what how long until the original amount is essentially depleted?

Section 18.1

Radioactivity

• If the half life of Ra-223 is 12 days, how long will it take for a sample containing 1.0 mol of Ra-223 to reach a point where it only contains 0.25 mol of Ra-223?

Section 18.1

Radioactivity

• “Glow in the dark” time pieces used to made with Ra-228 paint. Assuming that 8.0 X 10-7 mol of Ra-228 was originally used to paint the number 3 and that many years later only 1.0 X 10-7 mol of Ra-228 remained on the 3, approximate the age of the watch.

• ½ life Ra-228 = 6.7 years

Section 18.1

Radioactivity C. Detection of Radioactivity and the Concept of Half- life

• Achilles and the tortoise

• “In a race, the quickest runner can never overtake the slowest, since the pursuer must first reach the point whence the pursued started, so that the slower must always hold a lead.”—Aristotle, Physics VI:9, 239b15

• Give a tortoise a head start……

• The answer is obvious if you consider infinite converging theories…

Section 18.1

Radioactivity

1. To learn the types of radioactive decay 2. To learn to write nuclear equations for

radioactive decay 3. To learn how one element may be changed to

another by particle bombardment 4. To learn about radiation detection instruments 5. To understand half-life 6. Work Session: Page 869 # 11, 13, 18, 19, (B

particle is e-), 27 (more or less)

Objectives Review

Section 18.2

Application of Radioactivity

1. To learn how objects can be dated by radioactivity

2. To understand the use of radiotracers in medicine

Objectives

Section 18.2

A. Dating by Radioactivity

• Originated in 1940s by Willard Libby

– Based on the radioactivity of carbon-14

Radiocarbon dating – not a precursor to chemistry.com

• Used to date wood and artifacts• What kind of decay is this?

Section 18.2

A. Dating by Radioactivity

• Radiocarbon dating C-14 is formed in the atmosphere by invading neutrons from space

• 147 N + 1

0 n 146 C + 1

1 H • Over time, an equilibrium has resulted between the

formation and decay of C-14 resulting in a constant concentration on the atmosphere.

• As plants photosynthesize, their C-14 content is the same as in the atmosphere.

• When a plant stops photosynthesizing, the C-14 begins to decay with ½ life = 5730 years.

• A wooden bowl with ½ the concentration of C-14 as in the atmosphere is approx 5730 years old…

Section 18.2

B. Medical Applications of Radioactivity

• Radioactive nuclides that can be introduced into organisms and traced for diagnostic purposes.

• PHeT Dating

Radiotracers

Section 18.2

550 – 750 AD Basketmakers

750-1100 AD Developmental Pueblo

1100 – 1300 AD Great Pueblo Period

Section 18.2

1. To learn how objects can be dated by radioactivity

2. To understand the use of radiotracers in medicine

3. Work Session: Attached to the last work session

Objectives Review

Section 18.3

Using the Nucleus as a Source of Energy

1. To introduce fission and fusion as sources of energy

2. To learn about nuclear fission and how a nuclear reactor works

3. To learn about nuclear fusion

4. To see how radiation damages human tissue

5. To use Einstein’s energy equation E = mc2

Objectives

Section 18.3

A. Nuclear Energy

• Two types of nuclear processes can produce energy

– Splitting a heavy nucleus into 2 nuclei with smaller mass numbers - fission (take apart) (Nuclear Power Plants)

– Combining 2 light nuclei to form a heavier nucleus - fusion (put together) (Sun’s Rx)

Section 18.3

B. Nuclear Fission

• Releases 2.1 1013 J/mol uranium-235

• Each fission produces 3 neutrons

Section 18.3

B. Nuclear Fission

• Chain reaction – self sustaining fission process caused by the production of neutrons that proceed to split other nuclei

• Critical mass – mass of fissionable material required to produce a chain reaction

Section 18.3

Using the Nucleus as a Source of Energy B. Nuclear Bomb?

Section 18.3

B. Nuclear Fission

Section 18.3

C. Nuclear Reactors

Section 18.3

C. Nuclear Reactors

Reactor core control

PHeT Fission

Section 18.3

C. Nuclear Reactors Potential Hazards?

• Three Mile Island Middleton, Pa 4-1-79

• Partial meltdown• Chernobyl Ukraine,

Russia, 4-27-86• Complete meltdown• Approx 600,000 highly

exposed people• Covered by concrete

sarcophagus• Still Radioactive….

Section 18.3

• Fukushima, Japan 1, 2• March 11, 2011 Triple

Meltdown after Tsunami

• August 2013 radioactive radiation still leaking into the ocean

• June 2013 Cs-134 Vancouver , BC concs 0.9 Bequerels/m3

• Safe Drinking Water standard 28 Beq/m3

Section 18.3

ICBM Missile

Section 18.3

C. Nuclear Reactors and Nuclear Waste

• In the United States today, over 161 million people reside within 75 miles of temporarily stored nuclear waste.

• This opinion is reflected in a 1990 report from the National Research Council of the National Academy of Sciences, which states that there is “a worldwide scientific consensus that deep geological disposal, the approach being followed by the United States, is the best option for disposing of highly radioactive waste.”

• http://www.ocrwm.doe.gov/factsheets/doeymp0338.shtml

• Earthquake?

Section 18.3

D. Nuclear Fusion

• Process of combining 2 light nuclei

• Produces more energy per mole than fission

• Powers the stars and sun

Section 18.3

D. Nuclear Fusion

• Requires extremely high temperatures

• Currently not technically possible for us to use as an energy source

• 2 million Kelvins!!

• Cold Fusion claim…late 1980’s• http://www.physorg.com/news131101595.html• http://en.wikipedia.org/wiki/Cold_fusion

Section 18.3

D. Energy Calculations

• Einstein’s energy equation E = mc2

• E = energy released (J)

• m = mass difference between reactants and products (kg)

• C = speed of light 3.0 X 10 8 m/s

• Law of conservation of mass?

• Beam me up, Scotty…

Section 18.3

• How much energy will be released when 1 mole of Ra-226 decays by alpha emission to produce Rn-222. [J = kg(m2/s2)]

• 22688 Ra 222

86 Rn + 42He

• 1 mole 1 mole + 1 mole

• 226.0254 g 222.0175g + 4.0026g

• 0.0053g difference- where’d it go?

• E = mc2

Section 18.3

• 0.0053g difference- where’d it go?

• E = mc2

• E = ?

• m = 0.0053g = kg

• C = 3 X 108 m/s

• E = mc2 = (5.3 X 10-6kg)(3 X 108 m/s)2

• E = 4.8 X 1011 J

Section 18.3

E. Effects of Radiation

• Energy of the radiation

• Penetrating ability of the radiation

• Ionizing ability of the radiation

Factors Determining Biological Effects of Radiation

• Chemical properties of the radiation source

Section 18.3

• Alpha- stopped by skin• Beta- cm depth • Gamma- highly penetrating• Ionization?• Alpha- highly• Gamma-occasional ionization• Kr-85 and Sr-90 both Beta source• Kr-noble, pass through system• Sr- similar to Ca- leukemia, bone

cancer

Section 18.3

• Government Recommendation: < 500 mrems/yr• X ray- dental…20 mrems• X ray- chest…50 mrems• Smoking…• 10,000 mrems/yr• Idaho Daily EPA RadNet Monitoring

Section 18.3

1. To introduce fission and fusion as sources of energy

2. To learn about nuclear fission and how a nuclear reactor works

3. To learn about nuclear fusion 4. To see how radiation damages human

tissue 5. To use Einstein’s energy equation E = mc2

6. Work Session: Review Page 870 # 35

Objectives Review

Section 18.1

Radioactivity C. Detection of Radioactivity and the Concept of Half- life • Scintillation counter – instrument which measures the

rate of radioactive decay by sensing flashes of light that the radiation produces in the detector

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