Bellwork- List three to five things you know or want to know about nuclear chemistry. Be ready to share. 

CHEMISTRY 1 Unit 17 Nuclear Chemistry Chapter 21

NUCLEAR CHEMISTRY In 1896- Antoine Becquerel discovered radioactivity. He accidentally left uranium ore on top of photographic plates. They became fogged from exposure to the radiation. Becquerel had two graduate students: Marie and Pierre Curie.

Question What did the uranium do to the photographic plates?

Radioactivity- the property by which uranium gives off rays. Radiation-penetrating rays emitted by a radioactive source. In 1903, the Curies and Becquerel won Nobel prizes for this discovery. Marie Curie is still the only woman to win the Nobel prize in Chemistry and Physics

Radioisotopes –are radioactive isotopes that have unstable nuclei. The stability of a nucleus is determined by its ratio of protons to neutrons. An unstable nucleus loses energy by spontaneously emitting radiation. This is radioactivity. *All nuclides with atomic numbers greater than or equal to 84 are unstable. *Light nuclides are stable when the neutron/proton ratio = 1. *Heavier nuclides are stable when the neutron/proton ratio is greater than 1. *Nuclides with even numbers of protons and neutrons are more stable than those with odd numbers.

Question Would plutonium be stable or unstable? Why or why not?

Types of Radiation 1. alpha () emission -helium nuclei ( ) emitted from a radioactive source 2 protons & 2 neutrons = 4 2+ charge Don’t travel far and are not very penetrating (stopped by a sheet of paper) Can’t penetrate skin, but dangerous if ingested Very common with heavy nuclides He

Examples: U  ___ + He Ra  Rn + He Th 238 92 222 86 Mass # = # protons + # neutrons 238 U  ___ + He Th 92 Atomic # 222 Ra  Rn + He 86 Law of conservation of mass

2. Beta Radiation - fast moving electron formed by the decomposition of a neutron of the atom. (net effect: neutron changes into a proton). Much smaller than an alpha particle Symbol is beta or β Charge is negative 1 Much more penetrating than alpha particles Stopped by aluminum foil or thin pieces of wood

3. Gamma emission – electromagnetic radiation (high energy) emitted from a nucleus as it changes from an excited state to a ground energy state. Often emitted along with alpha or beta radiation Symbol is gamma or γ Has no charge and no mass High energy photon Extremely penetrating, very dangerous Stopped somewhat by several feet of concrete or several inches of lead.

4. Positron emission – particle with the mass of an electron but with a positive charge. • antimatter

Let’s Sum it Up! Type of radiation Symbol Symbol with mass and charge Penetration Alpha α He Low Beta β e Medium Gamma γ High Neutron n Very High Positron Let’s Sum it Up!

Question When nuclear power was first developed, people thought they could protect themselves from a nuclear blast by hiding in their basements. Was this a correct assumption?

e Co Ni + ____ Am Np + ____ He Th He + ____ N + ____ C + H Ra n Let’s Practice Writing Nuclear Equations: +1 60 26 e Co Ni + ____ Am Np + ____ Th He + ____ N + ____ C + H 60 27 4 2 He 241 95 237 93 226 88 Ra 230 90 4 2 1 n 1 14 7 14 6

Nuclear Transformation (Transmutation) process of nuclear decay changing one element into another. Bombarding with alpha particles Bombarding with neutrons

Bellwork Complete the following nuclear equation. 2 10n + 13555Cs  _______ + 0-1e

This is the way that heavy elements are created that are added onto the periodic table. How far will it go? Only time and our technology can tell! Nuclear Transformation (Transmutation)- changing one element into another. bombarding with alpha particles Bombarding with neutrons N + He  O + H U + n  U

Half-life (t1/2) Half-life: The time required for one half of a radioisotope to emit radiation and decay to products. The longer the half-life, the more stable the isotope. Half-life varies from fractions of a second to millions of years.

Examples 4 half lives X 10 min/half life = 4 half lives 40 min. Nitrogen-13 decays to carbon-13 with a half-life of 10 minutes. How long is 4 half lives? 4 half lives X 10 min/half life = 4 half lives 40 min. 10 min/half life

If you start with 2.00 g of nitrogen-13 how many grams will remain after 4 half lives?

57.2 yr = 4 half-lives 14.3yr / half-life 4.0 g 2.0 g 1.0 g 0.50 g Phosphorous-32 has a half-life of 14.3 yr. How many grams remain after 57.2 yr from a 4.0 g sample? 57.2 yr = 4 half-lives 14.3yr / half-life 1 2 3 4 4.0 g 2.0 g 1.0 g 0.50 g 0.25 g

Decay series - series of nuclear decays that eventually lead to a stable product. The heaviest nuclide of each decay series is called the parent nuclide. The nuclides produced by its decay series are called daughter nuclides. The uranium-238 series (found in most textbooks) is a common example. It shows the eventual decay into lead.

U-238 Decay Series

Carbon-14 dating How does Carbon Dating work? Carbon-14 is continually produced in the atmosphere when high energy neutrons from outer space collide with nitrogen-14 in the air.   Carbon-14 combines with oxygen to form CO2 which is incorporated into plant materials. As long as the plant or animal is alive, decaying carbon-14 is continuously replaced. After death, the carbon-14 decays at a steady rate. Carbon-14 decays to Nitrogen-14

The proportion of carbon-14 in the atmosphere is relatively constant The proportion of carbon-14 in the atmosphere is relatively constant. The carbon-14/carbon-12 ratio is used to identify the age of wood, cloth and other organic artifacts. The half-life of carbon-14 is 5,730 years. • Only works for organic materials • Adjusted for change in percent C-14 over the years C  e + N

Carbon-14 Dating and the iceman: The current activity per gram of Carbon-14 was half what it would be if the Iceman were alive. Since the half-life of carbon-14 is about 5700 years, the Iceman's remains are about 5700 years old.

Example To have ¼ remaining, 2 half lives have passed. 2 X 5730 yr = If the C-14 in a sample is only 1/4 what it is in living organisms, how old is the object? To have ¼ remaining, 2 half lives have passed. 2 X 5730 yr = 11,460 yr.

Bellwork Polonium-318 has a half-life of 3.05 minutes. How many grams remain after 18.3 minutes from a 18.0 g sample?

Transuranium elements Elements with atomic numbers above 92. They don’t occur in nature Are radioactive

Particle accelerators This is Fermi Labs in Batavia, Illinois. Particle accelerators “______________” super colliders subatomic particles are accelerated by magnetic fields to travel at close to the speed of light and smash a nucleus. TAMU has a small particle accelerator (cyclotron) -sort of like a atom race track atom smashers

Fission- splitting a heavy nucleus into two nuclei with smaller mass numbers. used for nuclear energy production of neutrons causes a chain reaction (which must be controlled) 1 kg of uranium-235 is equivalent to 20,000 tons of dynamite n + U  Ba + Kr + 3 n

Fission in a nuclear reactor is carefully controlled Fission in a nuclear reactor is carefully controlled. Much of the energy is heat. This energy is used to produce steam and subsequently, electricity. A coolant, (usually water), is needed. The water (or carbon) also acts as a moderator. It slows the neutrons down so that they can be captured by the U-235 fuel. Control rods made of cadmium are present to absorb excess neutrons to slow down the reaction. They can be raised or lowered into the reactor core.

Chernobyl A reactor at the plant exploded on April 26, 1986; as a result of the explosion and ensuing fire, clouds of radioactive particles were released. There were 56 direct deaths and it’s estimated that as many as 9,000 people, among the approximately 6.6 million most highly exposed, may die from some form of cancer.

The area of Russia around the Chernobyl plant experienced an increase in many health problems. -thyroid cancers increased due to intake of radioactive iodine -tumors increased due to inhalation of radioactive dust -birth defects and malformations increased in people who were young adults at the time of the meltdown.

SEE THE DIFFERENCE?

Fusion- combining two light nuclei to form a heavier, more stable nucleus Stars produce their energy this way Currently, high temperatures are necessary in order to initiate fusion This is a possible future energy source 4 H + 2e  He + energy

Manhattan Project Developing a nuclear weapon… Atomic Bomb (fission reaction) Hydrogen Bomb (fission reaction causes a fusion reaction) This is a thousand times more powerful than fission bombs

“Little Boy” dropped on Hiroshima on August 6, 1945 Before and After

“Fat Man” dropped on Nagasaki on August 9, 1945 Two days before Three days after

In Hiroshima, approximately 70,000 people were killed as a direct result of the blast, and a similar number were injured. A great number more would later die as a result of nuclear fallout and cancer. Unborn babies died or were born with deformities. Clothing was burned into the skin. An estimated 40,000 people were killed outright by the bombing at Nagasaki, and about 25,000 were injured. Many thousands more would die later from related injuries, and radiation sickness from nuclear fallout.

Nagasaki, Japan

H-Bomb

After being buried for about 1,000 years most of the radioactivity will have decayed

Units of radiation Rad- absorption of 0.01J/kg body tissue Rem- n(# of rads) adjusts for relative effectiveness of the radiation in causing damage to humans. Background radiation  0.13 rem/yr Chest X-ray = 0.05-0.2 rem 0-25 rem causes no detectable damage. Ionizing Radiation – knocks electrons off some atoms of the bombarded substance to produce ions (,,, and X-rays)

Cell Phones??? Not ionizing radiation Headaches? Skin sensitivity?

Methods of detection: Geiger Counter - gas-filled metal tube to detect radiation primarily detects beta Scintillation Counter -specially coated screen to detect radiation can detect all types Film Badges detect beta and gamma

Radioisotopes in Research and Medicine: Tracers: Iodine-131 is used to check for thyroid problems Radioactive barium is used to check for digestive system problems. Cobalt-60 and Cesium-137 are used as radiation sources for cancer treatment.

Bellwork- Is alpha radiation dangerous? Why or why not?