Nuclear Chemistry PDF

CHEME - Chemistry for Engineers Nuclear Chemistry The nucleus does not strongly affect the chemistry of NUCLIDE is a nucleus with a specified number of the atom (bond making/breaking). However, the protons and neutrons (= a specific iso...

CHEME - Chemistry for Engineers Nuclear Chemistry The nucleus does not strongly affect the chemistry of NUCLIDE is a nucleus with a specified number of the atom (bond making/breaking). However, the protons and neutrons (= a specific isotope). The nucleus can undergo changes, which usually cause unstable nuclide is called the parent nuclide; the an element to change into another element. nuclide that results from the decay is known as the daughter nuclide. NUCLEAR CHEMISTRY is the study of reactions that involve changes in nuclear structure. RADIOACTIVITY is the spontaneous decomposition of atomic nuclei, which releases high-energy particles or rays. ATOM is the smallest unit of matter that retains all of ISOTOPES are nuclides that differ in number of the chemical properties of an element. neutrons only. They are distinguished by their mass numbers. ELECTRONS ( −10𝑒) are a type of subatomic particle with a negative charge. PROTONS ( 11𝑝) are a type of subatomic particle with a positive charge. Protons are bound together in an atom's nucleus because of the strong nuclear force. NEUTRONS ( 10𝑛) (bound into the atom's nucleus) are a type of subatomic particle with no charge (they are neutral). RADIOISOTOPE - every element has at least one isotope whose nucleus spontaneously decomposes. TYPES OF RADIOACTIVITY 1. ALPHA PARTICLE (𝛼) EMISSION It is the emission part of an alpha particle from an atom’s nucleus. The 𝛼 particle includes two protons and two neutrons and is much like Helium (He) nucleus 42𝐻𝑒. When an atom emits an 𝛼 particle, the atomic mass of an atom decreases by 4 units. 238 4 234 92𝑈 → 2𝐻𝑒 + 90𝑇ℎ 2. BETA PARTICLE (𝛽) EMISSION NUCLEONS two subatomic particles that reside in When an atom emits a 𝛽 particle, the mass of the the nucleus known as protons and neutrons. atom will not change. The atomic number will increase by one. ATOMIC NUCLEI consist of electrically positive 234 234 90𝑇ℎ → 91𝑇ℎ + −1𝑒 0 protons and electrically neutral neutrons. 3. GAMMA RAY (𝛾) EMISSION MASS NUMBER (A) is defined as the total number It involves the emission of electromagnetic energy of protons and neutrons in an atom. from an atom’s nucleus and often accompanies different types of nuclear decays. During gamma ATOMIC NUMBER (Z) is the number of protons in an radiation, no particles are emitted and thus it does atom. not cause the transmutation of atoms.  CHEME - Chemistry for Engineers Nuclear Chemistry 238 92𝑈 → 42𝐻𝑒 + 234 0 90𝑇ℎ + 2 0𝛾 STIMULATED NUCLEAR REACTIONS NUCLEAR FISSION: It is the type of reaction + 4. POSITRON (𝛽 ) EMISSION where the atom’s nucleus splits into smaller parts The emission of a positron from the nucleus. releasing a huge amount of energy in the process. 238 139 94 1 Positron emission is observed for nuclides in 92𝑈 → 56𝐵𝑎 + 36𝐾𝑟 + 2 0𝑛 which the n:p ratio is low. Positron decay is the conversion of a proton into a neutron with the NUCLEAR FUSION: It is a type of reaction where emission of a positron. two or more elements fuse together to form a larger 15 15 0 8𝑂 → 7𝑁 + +1𝑒 element, releasing a large amount of energy in the process. 2 3 4 1 5. ELECTRON CAPTURE 1𝐻 + 1𝐻 → 2𝐻𝑒 + 0𝑛 Electron capture occurs when one of the inner electrons in an atom is captured by the atom’s NUCLEAR TRANSMUTATION is the change of one nucleus. Electron capture occurs when an inner element into another by particle bombardment shell electron combines with a proton and is (neutron, α particle, proton, nucleus). Most of the converted into a neutron. The loss of an inner ~3300 known radioisotopes are made through artificial shell electron leaves a vacancy that will be filled nuclear transmutation in particle accelerators. All by one of the outer electrons. elements with atomic numbers greater than 92 40 0 40 19𝐾 + −1𝑒 → 18𝐴𝑟 (transuranium elements) have been artificially made. DETECTION OF RADIOACTIVITY GEIGER-MÜLLER COUNTER: High-energy particles ionize argon; argon ions can conduct electricity. SCINTILLATION COUNTER: Uses a substance that gives off light when struck by high-energy particles. THERMOLUMINESCENT DOSIMETERS: Electrons excited by high-energy particles are trapped in crystals, then heated to relax into ground state and emit light. HALF-LIFE: Time required for half of the original sample of nuclei to decay. NUCLEAR FISSION Half-life of 14C = 5715 years Occasionally, an atomic nucleus breaks apart into Atmosphere has constant amount of 146𝐶. smaller pieces in a radioactive process called 146𝐶 content in a living plant is constant due to spontaneous fission (or fission). Typically, the constant uptake of 146𝐶 𝑂2 by plant. daughter isotopes produced by fission are a varied At moment of death, plant 146𝐶 decays without mix of products, rather than a specific isotope as with replenishment. alpha and beta particle emission. Often, fission So 146𝐶 content of fossil tells how much time has produces excess neutrons that will sometimes be passed since the plant died (age). captured by other nuclei, possibly inducing additional radioactive events. Uranium-235 undergoes 𝐶𝐴 ln ( ) = 𝑘𝑡 spontaneous fission to a small extent. One typical 𝐶𝐴0 reaction is Question: The half-life of Zn-71 is 2.4 minutes. If one had 100.0 g at the beginning, how many grams would ** MAGIC NUMBERS be left after 7.2 minutes has elapsed? Nuclei with 2, 8, 20, 28, 50, or 82 protons or 2, 8, 20, 28, 50, 82, or 126 neutrons are more stable than with nuclei without these numbers  CHEME - Chemistry for Engineers Nuclear Chemistry EFFECTS OF DIFFERENT TYPES OF RADIATION DAMAGING EFFECTS OF RADIATION IONIZING POWER: ability of radiation to ionize molecules and atoms. More massive particles have more potential to interact with and ionize other molecules. PENETRATING POWER: ability of radiation to penetrate matter. Smaller particles can penetrate more deeply. TYPES OF RADIATION DAMAGES NUCLEAR MEDICINE APPLICATION ACUTE RADIATION DAMAGE: damage to cells RADIOTRACERS: radioactive nuclides that can resulting from exposures to large amounts of be put into organisms through food or drugs and radiation in short period of time. be traced for medical diagnosis. INCREASED CANCER RISK: Lower radiation doses over a longer period can cause damage to somatic cells and increase cancer risk. GENETIC DEFECTS: damage to DNA in reproductive cells that shows effect in offspring. Rem: A unit that indicates biological damage of radiation. ASSIGNMENT Identify which type(s) of radioactivity contribute to radiation damages such as acute radiation damage, RADIOTHERAPY: gamma rays are used to kill increased cancer risk, and genetic defects, and rapidly dividing cancer cells; patients undergoing indicate the rem of radiation exposure to manifest radiotherapy develop symptoms of radiation these radiation damages. Properly indicate sickness (vomiting, hair loss, skin burns). references.