Honors Chemistry Unit 12 Nuclear Chemistry

Nuclear Chemistry

• involves a change in the nuclear of an atom(protons/neutrons)

  • produce radiation

Radiation

• unstable nuclei undergo transmutations to emit decay particles

transmutation

one element turns into another element

isotope

atoms of thee same element that contain a different number of neutrons

Causes of Radioactivity

• overcrowding(too much stuff in nucleus)

• too many neutrons

• too many protons

Who is radioactive

• all atoms above atomic numbers 82 and any isotope in table N

Changes from Alpha Decay

• alpha particles(helium nucleus, 2p+, 2n0)

Changes from Beta Decay

• beta particle(aka e-) is 0 over -1 e or 0 over -1 B

Changes from Positron Emission

• 0 over +1 B or 0 over +1 e

• proton splits to form neutron and positron

Radioactive Decay

gamma radiation

• energy released by nuclear decay

• no mass and no charge(unaltered by magnetic field)

• cause cell damage or DNA mutations because of penetrating power

Nuclear Equations

• show a conservation of mass and charge in these transmutations

Natural Transmutations

radioactive decay caused by unstable nuclei(spontaneous change) with alpha, beta, positron, and gamma particles

Artificial Transmutation

bombarding the nucleus with high energy particles to force a transmutation with fusion or fission

Natural vs Artificial Transmutations

• natural has 1 nuclear undergoing decay

• artificial has 2 reactants

• particle accelerators can be used to increase the kinetic energy of a charged particle to allow it to penetrate the nucleus

Fission

• involves splitting a heavy nucleus to produce lighter nuclei

Fusion

• involves combining light nuclei to produce a heavier nucleus

Fusion and Fission and Energy

• in both, the total mass of the products is slightly less than the total mass of the reactants

• mass is converted into energy(E=mc²)

Fission vs Fusion

• both reactions release massive amounts of energy(fusion more than fission)

• nuclear fission reactions are used in nuclear reactors to produce power(radioactive waste is produced)

• nuclear fusion typically does not produce radioactive waste, but is in the sun

• fusion reactions are more difficult, as colliding two positive nuclei together needs a lot of kinetic energy

Fuel Rods

used as material for fission reactions

Control Rods

absorb neutrons to control the reaction

Moderators

slow down neutrons to control the reaction

Coolant

absorbs excess heat to prevent a meltdown

Meltdown

heat melts down the fuel rod exposing radiation

Half-Life

the amount of time it takes for half of a radioactive sample to decay

Constant of the half life equation

doesn’t depend on temperature, pressure or concentration

Normal Half Life Equation

Mo = Mr(2^a/h)

Half Life Equation for Number of Half Lifes

# of HL = time elapsed/HL

Half Life Equation for Half Life

HL = Age/exponent

B+ for Fe-55

When an atom of iron-55 decays it becomes an atom of manganese-55. What is the decay mode for Fe-55?

B- for Mg-27

Which particle is spontaneously released when a nucleus of Na-27 transmutes to produce a nucleus of Mg-27?

increases

What happens to the atomic number of an atom when it undergoes it releases an electron?

100g

If 12.5 grams of cesium-137 remained after 90.6 years, what was the mass of the original sample?

16 years

Calculate the half-life of a sample if 1/64 remains after 96 years

D. a proton

Which particle can be accelerated by an electric field?

A. a hydrogen atom

B. a helium atom

C. a neutron

D. a proton

B. fusion

For a given mass of reactants, the energy released is greatest for a reaction involving

A. slow oxidation

B. fusion

C. fission

D. rapid oxidation

D. production of energy by the Earth’s Sun

An uncontrolled chain reaction takes place during the

A. explosion of an atomic bomb

B. operation of a fission nuclear reactor

C. fusion of light nuclei into heavier nuclei

D. production of energy by the Earth’s Sun

B. absorb neutrons

Control Rods in nuclear reactors are commonly made of boron and cadmium because these two elements have the ability to

A. emit neutrons

B. absorb neutrons

C. decrease the speed of neutrons

D. increase the speed of neutrons

D. release larger amounts of energy

Compared to an ordinary chemical reaction, a fission reaction will

A. absorb larger amounts of energy

B. absorb smaller amounts of energy

C. release smaller amounts of energy

D. release larger amounts of energy

D. moderators

Which components of a fission reactor are used to slow neutrons during a fission reaction?

A. control rods

B. coolants

C. shields

D. moderators

1/2

Based on the selected radioisotopes chemistry reference table, what fraction of a sample of gold 198 remains radioactive after 2.69 days?

151 years

If a sample of cesium 137 is stored in a waste container in Yucca Mountain, how much time must elapse until only 1/32 of the original sample remains unchanged?

3. a positron

Which emission will be released from an unstable Fe-53 nucleus?

1. an alpha particle

2. beta particle

3. a positron

4. a proton

Americium-241

smoke detection

Hydrogen-3

used for radioluminescence in watches and other devices

Promethium-147

used in research, specialized atomic batteries, pacemakers, missiles, radios

Polonium-210

to remove static from photocopiers

Carbon-14

dating of organic remains

Uranium-238

dating of geological rock samples

Phosphorus-31/Sodium-24

used as tracer, X-rays, MRIs

Iodine-131

for the treatment and disorders of thyroid disorders

Cobalt-60

emits gamma radiation used in cancer treatments

Cesium-137

used for killing bacteria in food and beverages

Technetium-90

detecting brain tumors

Uranium-235/Uranium-233/Plutonium-239

fissionable fuel