Chapter

1
Chapter 4 Nuclear Chemistry

• The Heart of Matter

2
Nuclear Energy Good or Evil?

• Most current news is negative.
• Quiet and invisible mysterious.
• Mushroom clouds.
• Weapons of mass destruction.
• Power plant leaks.
• Nuclear contamination.
• The good news.
• Cancer cell death nuclear medicine.
• Radioisotopes agriculture crop production.

3
Review of the Atom

• First semester discussions nucleus (protons
  neutrons) electrons. Focused mostly on
  electrons determinants of the atoms chemistry.
• Perspectives.
• Atomic diameter 1,000 x its nucleus.
• A atom the size of our classroom its nucleus
  would be the size of the period in your text.

4
Review of the Atom

• Atomic density.
• One cm3 of water 1 gm.
• One cm3 of pure atomic nuclei 100 million
  metric tons!
• Atomic energy atomic nuclear reactions.
• Provide electricity and medical treatments for
  millions.
• Destroy millions by the power of its explosive
  power.

5
Atomic and Atomic Mass

• Atomic of protons.
• Atomic mass of nucleons (protons neutrons).
• Change the atomic change to a different
  element.
• Creation of radioactive phosphorous Aluminum
  alpha particles radioactive phosphorous which
  emits positrons (electron-like but opposite in
  charge).
• Al (13) He (2) P (15)

6
Natural Radioactivity Nuclear Equations

• Certain combinations of protons and neutrons are
  unstable nuclear decay emission of
  radioactive particles from the atomic nucleus.
• Radioactive decay is a random process, generally
  independent of outside influences.
• Isotopes nuclei of atoms differing in of
  neutrons.
• Radioisotopes nuclear decay radioactive
  particle emission.
• Radioactive decay unstable isotopes that loose
  some of their protons and/or neutrons.
• Nucloens of protons neutrons in an atomic
  nucleus.

7
Types of Radiation

• Natural radiation ores that naturally decay to
  other elements.
• Uranium-238.
• Artificial transmutation bombardment of stable
  nuclei with other subatomic particles radiation
  emission creation of one element from another.
• Induced radioactivity creation of a radioactive
  isotope after bombardment of stable nuclei with
  other subatomic particles.
• Creation of radioactive phosphorous Aluminum
  alpha particles radioactive phosphorous which
  emitts positrons (electron-like but opposite in
  charge).

8
Natural Radioactivity Nuclear Equations

• Balancing nuclear equations different from
  balancing chemical equations.
• Chemical equations
• Balancing with equal of elements on both sides
  of the equation.
• Balance of atoms.
• Nuclear equations
• Do no balance on both sides not equal of
  elements.
• Balance of nucleons (protons neutrons).
• Balancing atomic numbers ( of protons) and
  atomic mass numbers (number of nucleons).

9
Natural Radioactivity Nuclear Equations
The nuclear symbol. A spontaneous decay giving
off alpha (a) particles ( helium nuclei) alpha
decay. Radium-266 decays to
Radon-222
The nuclear symbol gives the atomic number to the
lower left of the element symbol and the mass
number to the upper left of the element symbol.
In chemical equations the charge is to the upper
right and the number of atoms in a compound is to
the lower right.
10
Natural Radioactivity Nuclear Equations
The nuclear symbol. Beta decay the spontaneous
giving off of a beta (ß) particles equivalent
of an electron (e). Hydrogen-3 (tritium) decays
to Helium.
The nuclear symbol gives the atomic number to the
lower left of the element symbol and the mass
number to the upper left of the element symbol.
In chemical equations the charge is to the upper
right and the number of atoms in a compound is to
the lower right.
11
Natural Radioactivity Nuclear Equations
Nuclear emission of (a) an alpha particle and (b)
a beta particle.
A Plutonium -239 decays to U-235 with alpha
emission and C-14 decays to N-14 with beta
emission.
12
Types of Radioactive Decay Radiation

• Alpha loss of helium alpha particle.
• Beta electron loss beta particle.
• Gamma emission of a high-energy photon with no
  charge or mass.
• Emitting atoms do not change but become less
  energetic.
• Photon a bundle of energy of insignificant mass
  which represents visible light and all kinds of
  other electromagnetic radiation.

13
Types of Radioactive Decay Radiation

• Radioactive decay that results in a decrease of 1
  in atomic (of protons), but no change in
  atomic mass ( of nucleons). Two different
  pathways achieve these phenomina.
• Positron emission (ß) particle equal in mass
  but opposite in charge to an electron.
• Proton (p) changes into a neutron, stays in the
  nucleus, and an emitted positron nucleus with
  one more neutron and one less proton same
  atomic mass number ( of nucleons) but 1 less
  atomic ( of protons) .
• Positron electron 2 gamma photons

14
Types of Radioactive Decay Radiation

• Radioactive decay that results in a decrease of 1
  in atomic ( of protons), but no change in
  atomic mass ( of nucleons). Two different
  pathways achieve these phenomina.
• Electron capture (EC) electron from frst or
  second shell enters nucleus.
• Outer electron drops to lower energy level to
  occupy that of lost electron x-radiation given
  off.
• Captured electron in nucleus proton one
  additional neutron and one less proton.

15
Types of Radioactive Decay Radiation
Nuclear change accompanying positron emission and
electron capture.
Positron emission and electron capture result in
the same products.
16
Types of Radioactive Decay Radiation
Radioactive decay and nuclear change.
These five nuclear processes are the most common.
17
Types of Radioactive Decay Radiation
Nuclear Symbols for Subatomic Particles
Nuclear Symbols for protons, neutrons, electrons,
positrons, alpha particles, beta particles and
gamma rays.
18
Half-Life

• Radioactive decay deals with large numbers of
  atoms making the process of radioactive decay
  more predictable.
• Half-life period of time required for one-half
  of the original numbers of atoms to undergo decay
  forming a new element.
• The half-life of an element can be very long
  (millions of years) or extremely short (tiny
  fractions of a second).
• It is impossible to say when all the atoms of a
  radioactive isotope will have decayed.
• Activity usually gone after 10 half-lives
  1/1000 of original activity remains.
• Calculation of the fraction of remaining original
  isotope 1/2n
• n number of half lives.

19
Half-Life
The half-life graph (T1/2) graph of radioactive
tritium.
The half-life graph (T1/2) graph of radioactive
tritium. Half of the tritium decays each half
life.
20
Radioisotopic Dating

• Principle.
• Age of rocks and archeological artifacts can be
  determined by use of isotope half-lives.
• Uranium-238 decays to lead-206 with a half-life
  of 4.5 billion years.
• Age of a substance (rock) relative amounts of
  uranium-238 and lead-206.
• Earths age rocks dated to 3.5 to 4.5 billion
  years old.

21
Controversies Settled By Radioisotopic Dating

• Shroud of Turin.
• Christs burial cloth? Claims since 1350 AD.
• Carbon-14 dating cotton fibers of cloth only
  800 years old.
• Dead Sea Scrolls dated to be 2000 years old
  authentic records.
• Age of brandies very expensive if 10-50 years
  old.
• tritium dating used.

22
Uses of Radioisotopes

• 3000 known radioisotopes produced mainly by
  artificial transmutation from stable isotopes.
• Tracers isotopes that can be easily traced
  particularly if they are radioactive.
• Pipe leaks under concrete sensed by a Geiger
  counter.
• Agriculture effectiveness of a fertilizer to be
  taken up by plants (radioactive phosphorous
  uptake) .
• Medicine
• Food preservation kill microorganisms
  responsible for spoilage by radiation.
• Harmful effects on consumers?
• No residual radiation.

23
Uses of Radioisotopes
Gamma radiation delays the decay of mushrooms
Radiation destroys microorganisms that cause
spoilage. Although controversial, there is no
good evidence that this process is dangerous.
24
Uses of Radioisotopes
A painting seen as usual and as a radiograph.
Saint Rosalie Interceding for the Plague-stricken
of Paermo (van-Dyke) shown as is and as a
radiograph.
A radiograph of a famous painting shows that the
canvas had previously been used for an earlier
painting.
25
Uses of Radioisotopes
Diagnostic test of blood flow by tecnatium-99m.
Testing blood flow through a healthy (left) and
damage heart (right).
Tc-99m emits gamma rays which can be detected.
The flow of blood can be studied.
Since Tc-99m emits only gamma rays which are
fairly harmless and very penetrating, it can be
used in diagnosis with a minimum of intrusive
procedures.
26
Uses of Radioisotopes
PET (Positron Emission Tomagraphy).
a) Patient in position for PET (Positron Emission
Tomography) and (b) image created by CT
(computerized tomography). Looking through the
skull into the brain at a pituitary tumor.
PET uses radioisotopes while CT uses X-rays.
27
Radiation and Us

• Ionizing radiation radiation can knock out
  electrons from atoms producing ions (charged
  atoms) which damages cells.
• Radiation damage to cells.
• Ions unnatural capture of electrons
  disruption of chemical reactions.
• Water changes to hydrogen peroxide highly
  reactive basis for neutron bomb.
• DNA damage mutations.

28
Radiation and Us

• Penetrating power of radiation penetration
  tissue damage.
• Quiet and invisible.
• Mass related to penetrating ability mass penetration.
• Alpha particles less penetration 4µ mass.
• Beta particles almost massless electrons more
  penetrating.
• Gamma rays most penetrating have no mass.
• Speed of particle - speed energetic
  radiation . Penetrating power.

29
Radiation and Us
An analogy of radiation and ""bowling"" rocks
Shooting radioactive particles through matter is
like rolling rocks through a field of
bouldersthe larger rocks stop more quickly.
30
Radiation and Us
The relative penetrating powers of alpha, beta,
and gamma radiation. Radiation outside the body
behaves like diagram to right. Radiation inside
body has reverse effects larger particles, less
penetrating, cause great damage over small area
which must absorb it energy.
31
Energy From the Nucleus

• Release of nuclear energy.
• Nuclear fission splitting of heavy nuclei into
  smaller nuclei basis of atomic bomb.
• Nuclear fusion combining of light nuclei to
  form heavier ones.

32
Energy From the Nucleus

• Einstein and the equivalence of mass and energy.
• Einstein worked out the potential power of the
  nucleus in 1905.
• Mass-energy equation E mc2.
• E energy, m mass, and c speed of light.
• Energy and mass are the same thing.
• Chemical reaction giving off heat must also loose
  mass.
• Reaction energy must be massive if mass loss is
  to be measured energy given off by a nuclear
  explosion.
• Conversion of mass to energy.
• 1 gram of matter to energy enough heat to warm
  a home for 1000 years.
• Conversion is not complete only 1 in the
  explosion of a hydrogen bomb.

33
Energy From the Nucleus

• Where does the energy come from in nuclear
  fission as in the atomic bomb or from a nuclear
  power plant?
• It is locked within the nucleus as binding
  energy.
• Binding energy combining protons neutrons
  atomic nuclei formed mass converted to energy
  to bind the nucleons together.

34
Energy From the Nucleus
Nuclear binding energy in 42 He
The mass of the parts of a helium-4 nucleus is
more than the mass of a helium-4 nucleus.
The mass defect (the difference of mass between
the parts of the He-4 nucleus and the whole He-4
nucleus) is converted into energy by Einstein's
equation Emc2. This energy is the binding
energy 28.3 MeV!
35
The Building of the Bomb

• Preliminary Discoveries.
• 1934 Enrico Fermi and Emillio Serge (Italy)
  first elementary nuclear fission experiments,
  neutron bombardment of atoms to make elements of
  higher atomic number, puzzling results, U-93 to
  Np-93 but could not account for additional
  radiation.
• 1938 Otto Hahn and Fritz Strassman (German)
  repeated Fermi experiment that demonstrated the
  splitting of uranium into elements not accounted
  for.
• 1938 Lise Meitner (Jewish) who worked with Hahn
  in Berlin fled to Sweden is contacted by Hahn
  concerning his findings. She calculates the
  uranium atom was splitting into fragments.

36
The Building of the Bomb

• Preliminary Discoveries.
• 1938 Otto Frisch, Liess nephew visits her and
  carries findings back to the Niels Bohr
  laboratory in Copenhagen. Bohr carries
  information to physics meeting in US. Frisch
  names phenominon nuclear fission.
• 1938 Fermi wins Noble Peace Prize, wife Jewish,
  and they flee to the US to get away from fascist
  Italy and Musallini we acquire the best nuclear
  physicist.

37
The Building of the Bomb

• Preliminary discoveries.
• 1937 Leo Szilard, Jewish, flees to US, was
  first to realize that neutrons released in
  fission of one atom can trigger it in another
  leading to the concept of a nuclear chain
  reaction.
• 1939 Szilard prevails upon Einstein to write
  letter to President Franklin Roosevelt to act
  first before Germany acts to create a nuclear
  bomb.

38
The Building of the Bomb
The splitting of a uranium atom.
A slow neutron splits a U-235 nucleus into Sr-90
and Xe- 143.
A slow neutron splits a U-235 nucleus into Sr-90
and Xe- 143. More neutrons and gamma rays
(energy) are also produced.
39
The Building of the Bomb
Schematic representation of a nuclear chain
reaction.
Neutrons released in the fission of one U-235
nucleus can strike other nuclei, causing them to
split.
40
The Building of the Bomb

• The Manhattan project.
• Roosevelt bigins the most highly secret research
  project ever conceived with more scientific
  brainpower than any project to date.
• So secret that Vice-President Truman knew nothing
  until after Roosevelts death.
• Four goals of the project.
• How to sustain the nuclear fission chain reaction
  1942 by Fermis team at Un. Of Chicago slow
  neutrons down by graphite rods probability of
  uranium hits, 4 kg critical.
• How to enrich uranium-235, the rare fissile
  isotope Oak Ridge, Tennessee team.
• How to make plutonium-239, another fissile
  isotope, Glenn Seaborg and his team. Large
  reactors built near Hanford, Washington to
  produce enriched plutonium.
• How to build a bomb based on nuclear fission.
  Robert Oppenheimer and his team at Los Alamos,
  NM. By 1945 enough plutonium was made for a bomb.

41
The Building of the Bomb

• Bomb components.
• Subcritical fissal uranium-235.
• Neutron source.
• TNT charge forces all pieces together runaway
  nuclear chain reaction.

42
The Building of the Bomb

• 16 July 1945 first test of atomic bomb in NM.
• 6 August 1945 Little Boy, uranium bomb,
  dropped on Hiroshima 100,000 casualties.
• 9 August 1945 Fat Man dropped on Nagasaki.
• 14 August 1945 Japan surrenders.
• Radioactive Fallout.
• Nuclear winter.
• Neutron bomb kills human life, neutrons
  absorbed in water to H2O2, but leaves inanimate
  structures intact.