Name: _______________________________________ Period: ____________

Unit 15: Nuclear Chemistry Guided Notes

Introduction to Nuclear Chemistry

Nuclear chemistry is the study of the structure of ___________________________________________and the ___________________________ they undergo.

Characteristics of nuclear reactions:o Isotopes of one element are changed into isotopes of another _____________________________o Contents of the __________________________ changeo Large amounts of _________________________ are released

Chemical Reactions Nuclear Reactions__________________________ are broken ______________________ emit particles and/or rays

Atoms are rearranged Atoms change into atoms of a different _________________________________

Involves ____________________________ electrons Involves __________________, _________________, and/or _______________________

______________________________ energy changes ______________________________ energy changes

____________________________________– process by which atoms give off rays or particles ____________________________________– the penetrating rays and particles emitted by a radioactive source

The Discovery of Radioactivity (__________-___________)

Roentgen found that invisible rays were emitted when electrons hit the surface of a fluorescent screen (discovered ________________________)

Becquerel accidently discovered that phosphorescent __________________________ rock produced spots on photographic plates (discovered ___________________________________)

Marie and Pierre Currie:o isolated the components emitting the rays (uranium atoms) o identified 2 new elements, _____________________ and _____________________ on the basis of their

radioactivityo These findings contradicted _______________________________ theory of indivisible atoms.

Review of Atomic Structure

Nucleus Electron CloudMajority of the __________________________ of the atom (99.9%)None of the _____________________________ of the atom (0.01%)

None of the _____________________________ of the atom (0.01%)Majority of the __________________________ of the atom (_____________________ times the size of the nucleus)

______________ (p+) and ______________ (n0) ______________(e-)

______________________ charged ______________________ charged

__________________________________ force holds the protons together

Weak _____________________________ force between negatively charged electrons and positively charged nucleus

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___________________________ – particles found in the nucleus of an atom

o neutrons and protons The nuclear symbol consists of three parts:

o Element symbolo Atomic number (Z) – number of _________________________

in the nucleus o _____________________ number (A) – sum of the number of

protons and neutrons Also written as the element name dash (-) mass number (example: ____________________________________) _____________________________ – each unique atom Ion- an atom with a _______________________________

Radioactivity

Isotopes– atoms of the same element with different numbers of _________________________________ Radioisotopes– isotopes of atoms with ___________________________ nuclei (too many or too few neutrons) Radioactive decay– when unstable nuclei lose energy by emitting ___________________________________ to

become more stableo This is a spontaneous reaction (happens on its own)

Nuclear Stability

Elements with atomic #s ______ to ______ are very stable. o Isotope is completely stable if the nucleus will not spontaneously __________________________.o ______:______ ratio of protons:neutrons (p+; n0)o Example: Carbon – 12 has ______ protons and ______ neutrons

Elements with atomic #s ______ to ______ are marginally stable.o ______:______ ratio of protons:neutrons (p+:n0)o Example: Mercury – 200 has ______ protons and ______ neutrons

Elements with atomic #s _________________ are unstable and radioactive.o Examples: Uranium and Plutonium

Nuclear Reactions

Types of Nuclear Reactions:o ___________________________________________ – alpha and beta particles and gamma ray emissiono Nuclear ___________________________________________________ - emission of a proton or neutron

Transmutation the conversion of an atom of one element to an atom of a different _______________________.o Usually occurs by radioactive decay

Nuclear equation – shows the radioactive decomposition of an element

Alpha Radiation

Composition – Alpha particles, same as a __________________________________ nuclei Symbol – Helium nuclei, ________________, α Charge – ________________

o Deflected towards a _________________________________ charged plate Mass – ______ amu Approximate energy – 5.0 MeV Penetrating power – ________________ (0.05 mm body tissue)

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Shielding – _______________________________________________________________ Alpha Decay Equations

o Step 1: Write the element that you are starting with followed by the yields symbol.o Step 2: Write the alpha particle as a producto Step 3: Determine the other product using atomic #.o Step 4: Determine mass and ensure everything is balanced.o (Net effect is loss of __________ in mass number and loss of ___________ in atomic number.)

Example 1: Write the nuclear equation for the radioactive decay of polonium – 210 by alpha emission. ___________________________________________________________________________________________

Example 2: Write the nuclear equation for the radioactive decay of radium – 226 by alpha emission. ___________________________________________________________________________________________

Beta Radiation

Composition – Beta particles, same as a fast moving __________________________________ A neutron is converted to a ______________________ an a _________________________ particle Symbol – e--, ________________ Charge – ________________

o Deflected towards a _________________________________ charged plate Mass – ______ amu Approximate energy – 0.05 – 1 MeV Penetrating power – ________________ (4 mm body tissue) Shielding – _______________________________________________________________ Beta Decay Equations

o Same steps as alpha equations except use a beta particle o (Net effect is ______________ change in mass and an addition of ______ in atomic number.)

Example 3: Write the nuclear equation for the radioactive decay of carbon – 14 by beta emission. ___________________________________________________________________________________________

Example 4: Write the nuclear equation for the radioactive decay of zirconium – 97 by beta decay. ___________________________________________________________________________________________

Gamma Radiation

Composition – gamma, High-energy electromagnetic radiation or high energy ____________________________ Usually accompanied by ______________________ and _________________________ radiation Symbol – ______________________________ Charge – ________________ Mass – ______ amu Approximate energy – 1 MeV Penetrating power – ________________ (penetrates body easily) Shielding – _______________________________________________________________ Beta Decay Equations

o Steps: include alpha and/or beta, and gamma decay Example 5: Write the nuclear equation for the radioactive decay of uranium – 238 by gamma decay

accompanied with alpha decay. _________________________________________________________________

Type of Radioactive Decay Particle Emitted Change in Mass # Change in Atomic #

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Alpha

Beta

Gamma

______________________________________________: when a substance undergoes a series of nuclear decay

Half-Life

Half-life is the ______________________

required for ____________________ of a radioisotope’s nuclei to decay into its products.

For any radioisotope,

# of ½ lives % Remaining100%

50%

25%

12.5%

6.25%

3.125%

1.5625%

Example 6: suppose you have 10.0 grams of strontium – 90, which has a half-life of 29 years. How much will be remaining after x number of years?

You can use a table:

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0 1 2 3 4 5 6 70

102030405060708090

100

Half-Life

# of Half-Lives

% R

emai

ning

# of ½ lives Time (years) Amount Remaining (g)01234

OR you can use an equation

Example 7: If gallium – 68 has a half-life of 68.3 minutes, how much of a 160.0 mg sample is left after 1 half life? ________ 2 half lives? __________ 3 half lives? __________

Example 8: Cobalt – 60, with a half-life of 5 years, is used in cancer radiation treatments. If a hospital purchases a supply of 30.0 g, how much would be left after 15 years? __________________________

Example 9: Iron-59 is used in medicine to diagnose blood circulation disorders. The half-life of iron-59 is 44.5 days. How much of a 2.000 mg sample will remain after 133.5 days? ______________

Example 10: The half-life of polonium-218 is 3.0 minutes. If you start with 20.0 g, how long will it take before only 1.25 g remains? ______________

Example 11: A sample initially contains 150.0 mg of radon-222. After 11.4 days, the sample contains 18.75 mg of radon-222. Calculate the half-life. ________________________

Nuclear Fission and Fusion

Nuclear Fission- _______________________________ of a nucleus

o Releases a lot of ______________________________

o ________________________ reactions occuro Produces radioactive _______________________o Usually fueled by

________________________________________o Example: ________________________ bomb,

nuclear reactors, nuclear ________________________________________

Nuclear Fusion- combining of two or more ____________________________________________________

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o Two _______________________ nuclei combine to form a ______________________ heavier nucleuso Does not occur under _______________________________ conditionso Releases a lot of ___________________________________ ( ___________________ than fission)o Not ____________________________________o Can cause ___________________________ reactionso Usually fueled by isotopes of ________________________________________________o Example: energy output of stars and the ______________________, and ____________________ bomb

(_______________ powerful than the atomic bomb)

AdvantagesFission Fusion

• Zero ____________________ pollution • Not a ___________________________________

so doesn’t contribute to climate change• Able to be _______________________________

• No radioactive ____________________________• Inexpensive

DisadvantagesFission Fusion

• Produces high level radioactive ________________________ that must be stored for ______________________________ of years.

• Meltdown causes _________________________ like in Japan and Chernobyl.

• Requires large amount of __________________________________ to start

• Difficult to _______________________________

Uses of Radiation

Radioactive ________________________________ Detection of _________________________________ Treatment of some malignant ______________________________ X-rays Radioactive ____________________________________ Everyday items: thorium–232 used in __________________________________ mantels, plutonium–238 used

in long-lasting ________________________________ for space, and americium–241 in ____________________________ detectors.

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