Presentation on theme: "Nuclear Chemistry. Section 1: Basic Definitions Nuclear Chemistry – The study of the atomic nucleus, its reactions and radioactivity Radioactivity – Spontaneous."— Presentation transcript:
Section 1: Basic Definitions Nuclear Chemistry – The study of the atomic nucleus, its reactions and radioactivity Radioactivity – Spontaneous emission of particles and/or energy during nuclear decay
Section 1, continued Nuclear Decay – Spontaneous disintegration of a nucleus – Results in a new element being formed – Occurs when particles and/or energy escape from an unstable nucleus – Releases large amounts of energy Radiation – Can refer to either the particles or energy released during nuclear decay
Section 2: Types of Radiation to Know Radiation Description Proton – Positively charged particle in the nucleus of the atom – Hydrogen nucleus – Most cosmic rays are protons traveling at the speed of light Neutron – Neutral particle in the nucleus of the atom Electron (Beta-minus particle) – Negatively charged particle that moves randomly in specific orbitals outside the nucleus of an atom Radiation Symbol
Section 2, continued Radiation Description Positron (Beta-positive particle) – Anti-matter electron – Same properties of an electron except it has a positive charge Alpha Particle – Helium nucleus – 1 st radioactive particle discovered by Ernest Rutherford Gamma Radiation – High energy electromagnetic radiation Radiation Symbol
Section 3: Properties of Certain Types of Radiation PropertyAlpha ParticleBeta-minus particle Beta-positive particle Gamma Radiation Charge +2+1n/a Speed Largest and slowest form of radiation Faster than alpha Faster than alpha (same as beta-minus) Speed of light Can be stopped by… Piece of paperPlastic, aluminum foil Thick lead or concrete
Section 4: Isotopes Same element, different number of neutrons There are 2 ways to identify isotopes: – Hyphen-Notation = element – mass # Example: oxygen – 16 – Chemical Configuration Example:
Section 4, continued Isotopes of hydrogen have special names Deuterium and tritium are radioactive; protium is not.
Section 4, continued Why are some isotopes radioactive and others are not? – The proton : neutron ratio determines whether an isotope is radioactive Elements with atomic # ≤ 20 prefer a 1 : 1 ratio Elements with atomic # > 20 prefer a 1 : 1.5 ratio Transuranium elements = – Elements with atomic # > uranium (92) – All are radioactive – In fact, all elements with atomic number > 83 are radioactive!
Section 4 Example Problems 1.Write the hyphen-notation and the chemical configuration for an iron atom that has 23 electrons and 32 neutrons.
3.Write the hyphen-notation and chemical configuration for the three isotopes of hydrogen. Assume each isotope is neutral.
Section 5: Use of Carbon-14 in Radiocarbon Dating
Section 6: Nuclear Reactions v Chemical Reactions Nuclear Reactions Forms a new isotope or different element Extremely large energy changes Energy comes from the binding energy of the nucleus Involves a change in the number of protons or neutrons Chemical Reactions Forms new substances based on the elements present in the reactants Small energy changes Energy comes from breaking and forming chemical bonds Involves valence electrons
Section 7: Writing Nuclear Reactions Steps 1.Set up 2 equations: one using the mass (top) numbers and the other using the atomic (bottom) numbers. 2.Calculate the missing mass number. 3.Calculate the missing atomic number. 4.Use the atomic/mass #s to determine the identity of the missing particle. Example
Section 8: Alpha Emission A helium nucleus (2 p, 2 n) is emitted from the nucleus Example: Alpha decay of 241 Am
Section 8: Beta Emission A neutron is converted into a proton and electron, then the electron (β- particle) is emitted Example: Beta decay of 14 C
Section 8: Positron Emission A proton is converted into a neutron and positron, and the positron is emitted from the nucleus Example: Positron Emission of 11 C
Section 8: Electron Capture The nucleus captures an electron and combines it with a proton to form a neutron Example: Electron capture by 7 Be
Section 8: Gamma Emission Gamma rays are emitted during nuclear reactions, either alone or with other types of radiation Gamma rays do NOT change the mass number or atomic number because they are energy not matter. γ ray
Section 9: Decay Series A series of nuclear reactions that occur until a stable nucleus is formed The first 4 nuclear reactions in the uranium-238 decay series are: 238 U 4 2 He + 234 Th 234 Th 0 -1 β + 234 Pa 234 Pa 0 -1 β + 234 U 234 U 4 2 He + 230 Th
Section 11: Nuclear Power Plant Containment Structure (A) -thick layers of concrete and steel to prevent radiation leakage Control Rods (B) -controls the rate of reaction; can be used to shut reaction down Reactor (C) -where the nuclear reactions take place Steam Generator (D) -nuclear reactions produce heat energy which is used to boil water Turbine (H) -steam runs the turbine, which causes the generator (G) to produce electricity Fuel Rods (K) -usually contain uranium-235; the fuel for the nuclear fission reaction Condenser (I) -sends cool water to the cooling tower (J) and reactor; vital to keep reactor from overheating
Section 11: Nuclear Power Plant A nuclear reactor is self-sustaining due to the chain reaction. The neutrons that are produced from one reaction cause a new fission reaction to occur.
Section 12: Nuclear Power (Fission) Pros and Cons Pros No air pollution No greenhouse gas emissions Low cost fuel because very little is needed Can be done at room temperature Cons Expensive to build and maintain Risk of accidents Security Thermal pollution (warm water into streams and rivers) Disposal of nuclear waste (must be buried for possibly thousands of years)
Section 14: Fusion Pros and Cons Pros Produces even more energy per gram of fuel than fission. Produces less nuclear waste than fission. Fusion fuel is easy to get. (Heavy hydrogen is found in water.) Cons Does not sustain a chain reaction. Requires extremely high temperatures (10 8 - 10 9 °C) and pressures. We do not have the technology to efficiently harness the energy produced by fusion or to contain a fusion reaction.