Unit 12 – Nuclear Chemistry

Part II Key Terms Alpha decay – spontaneous decay of a nucleus that emits a helium nucleus and energy Beta decay – spontaneous decay of a nucleus that emits an electron and energy Gamma decay – spontaneous decay of a nucleus that emits Isotope -Atoms of the same element with different numbers of neutrons Mass number -The total number of protons and neutrons in a nucleus Subatomic particles -The three kinds of particles that make up atoms: protons, neutrons, and electrons. Nuclear fission - Splitting of the nucleus into smaller nuclei Nuclear fusion - Combining nuclei of light elements into a larger nucleus Nucleon - a constituent (proton or neutron) of an atomic nucleus Radioactive decay - Spontaneous release of radiation to produce a more stable nucleus Radioactive isotope - An isotope (an atomic form of a chemical element) that is unstable; the nucleus decays spontaneously, giving off detectable particles and energy

 All nuclear reactions are based on Einstein’s Theory of Relativity  At speeds approaching the speed of light, energy and mass are interchangeable  E = mc 2 Energy = mass x (speed of light) 2  Mass can be converted to energy and vice versa Nuclear Reactions

There is a difference between the mass of an atom and the various particles that make up the atom This difference is called the mass defect of the atom This mass defect is the binding energy of the atom In nuclear reactions, the binding energy is released as energy (heat, light, or gamma radiation) and/or particles with measureable mass Mass Defect

Fission – Splitting of the nucleus into smaller nuclei Fusion – Combining nuclei of light elements into a larger nucleus Radioactive Decay – Spontaneous release of radiation to produce a more stable nucleus Types of Nuclear Reactions

Nucleus splits into smaller nuclei when struck by a neutron of sufficient energy Tremendous release of energy When controlled can produce huge amounts of power in nuclear reactors Naturally occurs in uranium and other ores in spontaneous fission Clean source of energy with no carbon footprint Produces radioactive nuclear waste with long term environmental and health considerations Fission

Fission Process

Fission and Nuclear Reactors

Lighter nuclei (such as hydrogen) combined to form heavier nuclei Tremendous release of energy 2 H + 3 H  4 He + 1 n + energy Deuterium Tritium Helium (occurs naturally in water) Powers the sun and stars No practical application to produce usable energy at this time Fusion

Fusion Process

Spontaneous release of radiation by unstable nuclei in order to increase stability Radiation can be either energy alone (gamma) or energy accompanied by release of a particle (all of the other forms of decay) Radioactive Decay

Alpha decay – release of alpha particle and energy Beta decay – release of beta particle and energy Gamma Emission – release of electromagnetic radiation (energy) Positron Emission – release of a positron and energy Electron Capture – absorption of and electron and release of energy Neutron Emission – release of a free neutron and energy Forms of Radioactive Decay

Typically found in heavier nuclei and the means to achieve stability is to reduce mass Nuclei shed mass in the form of a helium nucleus to become more stable Helium nucleus that is released is ionized and called and Alpha Particle Alpha Decay

Alpha Particle is positively charged (no electrons present) Alpha Particles are very massive, but travel slower (low penetrating power) Can cause significant tissue damage if not shielded Shielding can be accomplished with clothing or paper Alpha Decay (cont.)

Alpha Decay Process

Common in nuclei of any size where instability is caused by the number of neutrons Neutron decays into a proton and an electron Proton remains in the nucleus The electron leaves the atom and is called a Beta Particle Beta Decay

Beta Particle is negatively charged Mass of the nucleus is unchanged Beta particles have very low mass but are travelling at very high speed Beta particles can penetrate through the skin and cause deep tissue damage Beta Decay (cont.)

Beta Decay Process

Nucleus becomes more stable through the release of electromagnetic energy No change in mass No change in the element The Gamma radiation can be reduced by shielding, but Gamma radiation cannot be stopped Usually found with another type of decay, but not always Gamma Radiation

Radioactive Decay Type MassChargePenetrating Power Transmutation Alpha4 amuPositiveLowNew Element Formed Beta0 amuNegativeHighNew Element Formed GammaNone (no particle) NoneExtremely HighNo Radioactivity Decay Comparison

All nuclear reactions must conserve the overall mass of the particles involved in the reaction Two properties must be the same on both sides of a nuclear equation Total Mass Number – the sum of the mass numbers of all particles must be the same on both sides of the reaction Total Atomic Number – the sum of the atomic numbers of all particles must be the same on both sides of the reaction Nuclear Reaction Mass Conservation