NUCLEAR CHEMISTRY

DIFFERENTIATE BETWEEN FISSION AND FUSION. DESCRIBE THE NUCLEAR COMPOSITION OF UNSTABLE ISOTOPES AND THE RESULTING CHANGES TO THE THEIR NUCLEAR COMPOSITION. IDENTIFY TYPES OF NUCLEAR EMISSION, INCLUDING ALPHA PARTICLES, BETA PARTICLES, AND GAMMA RADIATION DIFFERENTIATE BETWEEN FISSION AND FUSION. IDENTIFY USES AND POSSIBLE NEGATIVE SIDE EFFECTS OF NUCLEAR TECHNOLOGY. COS 11.0, 11.1, 11.2, 11.3

WHAT YOU’LL LEARN Identify three types of nuclear radiation and their properties. Distinguish between fission and fusion, and provide examples of each. List and explain three beneficial uses and three possible risks of nuclear radiation. Contrast properties of radioactive and stable nuclei.

FYI: Historical Perspective Henri Becquerel 1896 - Discovers natural radioactivity

The discovery of radiation In 1896 Henri Becquerel made an important discovery. He accidentally had placed a piece of uranium ore on top of an unexposed photographic plate. Later, when the plate was developed, the image of the rock was found on the plate. Based on further experiments, he concluded that the plate had been exposed by rays given off by the uranium.

Madame Curie discovers Radium and Polonium Following Becquerel’s discovery, Marie Sklodowska Curie and her husband, Pierre Curie, attempted to isolate the “radioactive” material from the uranium ore. In doing so they discovered two new elements, Radium and Polonium, both of which were more radioactive than the original ore.

Ernest Rutherford Rutherford investigated this new property of matter and discovered that, in the process of emitting radiation, atoms of one element became atoms of another element. Today, we describe the process of an atom of one element becoming an atom of a different element as transmutation.

Rutherford discovered the different types of radiation Rutherford was the first to identify and name two different types of radiation given off when an atom of one element underwent transmutation and became an atom of another element. The two types of radiation he found were: The alpha particle (a) The beta particle (b) A third type of radiation that was discovered later is called: Gamma radiation (g)

Nuclear Reactions Involve changes in the composition of nuclei Accompanied by the release of tremendous amounts of energy Where does this energy come from?

Mass Defect Some of the mass can be converted into energy Shown by a very famous equation! E=mc2 Energy Mass Speed of light

Nuclear Fission The splitting of a heavy nucleus into lighter nuclei

Nuclear Fusion The combination of light nuclei to produce a heavier nucleus

Nuclear Radiation Chapter 9 Radioactivity: process by which an unstable nucleus emits one or more particles or energy in form of electromagnetic radiation. nuclear radiation: particles that are released from nucleus during radioactive decay. What makes the nucleus unstable?

The neutron-to-proton ratio determines the stability of the nucleus For low atomic #’s: Equal #’s of protons and neutrons Above atomic #20: More neutrons than protons Note: this stability has nothing to do with electrons and valence shells (we’re talking about nucleons)

Nuclides Different atomic forms of all elements (isotopes) Most small nuclides have equal # of protons and neutrons Some nuclides have “magic #’s” of protons and neutrons and are especially stable

Nuclei whose neutron-to-proton ratio is unstable undergo radioactive decay by emitting 1 or more particles and/or electromagnetic rays:

Type/ symbol Identity Mass (amu) Charge Penetration Alpha Beta Gamma Nuclei whose neutron-to-proton ratio is unstable undergo radioactive decay by emitting 1 or more particles and/or electromagnetic rays: Type/ symbol Identity Mass (amu) Charge Penetration Alpha Beta Gamma Proton Neutron helium nucleus 4.0026 2+ low electron 0.00055 1- low-med high energy radiation high proton, H nucleus 1.0073 1+ low-med neutron 1.0087 very high

Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the nucleus The nucleus opens, and protons and neutrons are rearranged The opening of the nucleus releases a tremendous amount of energy that holds the nucleus together – called binding energy “Normal” Chemical Reactions involve electrons, not protons and neutrons

Types of Radiation Alpha (ά) – a positively charged helium isotope - we usually ignore the charge because it involves electrons, not protons and neutrons Beta (β) – an electron Gamma (γ) – pure energy; called a ray rather than a particle

Penetrating Ability Can be stopped by a sheet of paper

Balancing Nuclear Reactions In the reactants (starting materials – on the left side of an equation) and products (final products – on the right side of an equation) Atomic numbers must balance and Mass numbers must balance Use a particle or isotope to fill in the missing protons and neutrons

ALPHA PARTICLES consists of two protons and two neutrons Composed of He nucleus atom w/ +2 charge Least penetrating type of radiation Can be stopped by a sheet of paper

BETA PARTICLES negatively charged electron emitted during certain types of radioactive decay Emitted at high speeds from nucleus

Beta decay

GAMMA PARTICLES gamma ray high-energy photon emitted by a nucleus during fission and radioactive decay Most penetrating type of radiation Does not have a charge nor mass

NEUTRON EMISSION consists of matter that is emitted from an unstable nucleus. Neutrons are able to travel farther through matter than either alpha or beta particles.

Nuclear Fission process by which a nucleus splits into two or more fragments and releases neutrons and energy. Produces nuclei of lower mass than reactants Used to produce nuclear power (electricity) Produces extremely toxic waste

Nuclear Fusion process in which light nuclei combine at extremely high temperature, forming heavier, more stable nuclei and releasing energy. Produces nuclei of higher mass than reactants Takes place in sun. Helium major by product

Beneficial Uses of Nuclear Radiation Smoke detectors small alpha-emitting isotope detects smoke particles in air. radioactive tracer: radioactive material that is added to a substance so that its distribution can be detected later. understand biochemical processes in plants. Radiotherapy: treatment that uses controlled doses of nuclear radiation for treating diseases such as cancer.

Nuclear Medicine: Imaging Thyroid imaging using Tc-99m

Food Irradiation Food can be irradiated with g rays from 60Co or 137Cs. Irradiated milk has a shelf life of 3 mo. without refrigeration. USDA has approved irradiation of meats and eggs.

Possible Risks of Nuclear Radiation Ionization change in number of electrons in an atom or molecule, causing the particle to be positively or negatively charged. Radiation sickness results from high levels of nuclear radiation. Dosimeter device that measures the amount of nuclear radiation exposure. Studies have shown a relationship between exposure to high levels of nuclear radiation and cancer.

Possible Risks of Nuclear Radiation Radon gas: colorless and odorless, produced by the decay of uranium-238 naturally occurs in soil and rock. Causes lung cancer