Nuclear+Chemistry

@http://explosm.net/comics/2334/ (provided by Goeff) **// Nuclear Chemistry //** (Chapter 20, pages: 859-884; Review sections: 2.2, 2.3 and 14.3)  Be able to define the concepts of: ¡ Nuclear chemistry- the chemical study of radioactive substances. the field of chemistry that stydies the stability of the nuclei and the radiation of particles and gamma rays --the study of the stability of the nuclei of an atom and the study of radiation ¡ Radiation- energy that is radiated or transmitted in the form of rays or wave particles. Surprisingly, we get more radiation from the soil than from the Sun. ¡ Radioactivity- the process of radiation happening.The emission of radioactive particles and/ or energy. ¡ Metastable atoms-An atom with an electron excited to an energy level where simple radiation is forbidden and thus the atom is momentarily stable. The presence of these metastable atoms in a discharge is the cause of several anomalous effects since in essence they are storing energy which can be released to other particles upon collision. The Penning effect is a result of the presence of metastable atoms. The emission of a gamma particle is usually the result of a metastable atom. ¡ Mass number-the biggest number. It is the number of protons and neutrons the element contains. Usually it is placed on top of the atomic number, but not always. ¡ Atomic number- the smallest number. It is the number of protons (Z) in an element. This number always remains the same for each element. ¡ Isotopes- one or more of two or more atoms with the same atomic number but with different number of neutrons. A wheighted average of all the naturally occuring isotopes is calculated for the atomic mass of an element. ¡ Nuclear decay- unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation. ¡ Emission-Atoms that are excited to a higher energy level can decay to a lower energy level by radiating alpha and beta particles, positrons, and gamma rays. ¡ Capture- Is a radioactive decay. The nucleus of the atom absorb all the electrons in the k or l shells and converts all the protons into neutrons. When this happens it lowers the atomic number by one and emits gamma radiation and neutrino. ¡ Alpha emissions - Is one of the five radioactive decays. This process is slow, and is about 5% to10% of the speed of light. The constant the Alpha-Particle Emission is 4/2He. This always appears on the product side. Elements with atomic numbers above 83 engage in alpha particle emissions because they are unstable. A nuclide of one element is transformed into a daughter nuclide. Example: (can be shielded by most materials: ie; glove) (only travels a few centimeters)

¡ Beta emissions- This emission always releases one electron. 0/-1 B is the constant. The nucleus ejects a beta particle at 90% the speed of light. A nuclide of one element is transformed into a daughter nuclide. (can be shielded by aluminum or other metals. higher frequency than alpha particles) ¡ Gamma emissions- A radioactive nucleus that undergoes gamma emission emits a very high energy photon. (Gamma ray). This is due to the nucleus reorganizing itself in a lower energy state, much like a photon is given off by an electron when it moves from a high energy level to a lower one. The nucleus does not change otherwise. A low energy daughter nuclide is formed. (very high frequency, can be shielded by lead or concrete) (Alpha and Beta emissions also release gamma particles) ¡ Electron capture- Electron capture is one process that unstable atoms can use to become more stable. During electron capture, an electron in an atom's inner shell is drawn into the nucleus where is combines with a proton, forming a neutron and a neutrino. The neutrino is ejected from the atom's nucleus. Example:
 * [|2613] [|Al] || + || [|e−] || → || [|2612] [|Mg] || + || [|νe] ||

¡ Positron emission decay of a proton into a neutron and a positron ¡ Decay series is a stepwise series to a stability. this is when a nuclei decay several time to get to a stability ¡ Ionizing energy- IE the minimum energy required to remove an electron from an atom in gas phase ¡ Free radicals- are molecular fragments having one or more unpaired electrons, they are usually short lived and highly reactive ¡ Mass defect- the difference between the actual mass of a nucleus and the mass calculated by summing the masses of the individual nucleons ¡ Binding Energy is the energy require to dismantle the nucleus into individual protons and neutron. it is express as a positive number. ¡ Fusion the process that liberate energy from the sun .it is energetically favorable to join lighter element like helium to form heavier ones that are more favorable for binding energy per nucleon ¡ Fission- the process in which a heavy nucleus divides to form smaller nuclei of intermediate mass and one or more neutrons. ¡ Nuclear chain reaction- a self-sustaining sequence of nuclear fission reactions. ¡ Critical mass- the minimum mass of fission-able material required to generate a self-sustaining nuclear chain reaction. ¡ Moderators-A material that limits the speed of neutrons, but the moderators does not split the nucleus into nuclei when it is surrounded by neutrons. ¡ Thermonuclear reactions ¡ Penetration/shielding

 Be able to recognize and use all radiation/radioactivity units 1 Ci = 3.7×10 10 Bq  1 Bq = 1 decay pre second Be able to represent isotopes using isotope notation notation of the isotope of an element has a subscript as its atomic number, and a superscript as its mass number.  Be able to describe the following radioactive events and identify the material used to shield each nuclear emission: ¡ **Alpha-Particle Emission** ( α), have high energy photon and short wavelenghth : The nucleus ejects a Helium alpha particle that travels 5 to 10 cm very slowly (approximately 5-10% the speed of light). Energy is released as gamma rays and the sum of the atomic numbers on one side equals the sum of the other side. The He nuclei is very large and alpha particle emission normally does not happen for nuclei smaller than z = 83. These particles are heavy and easy to shield. Sufficient shields are air, clothing, basically anything.

¡ **Beta-Particle Emission** ( β) : The nucleus ejects a beta particle (mass number of 0, charge of -1) in which results in the formation of a new atom. (K --> Ca). This travels at 90% of the speed of light and energy is released as gamma rays. Beta-Particle Emission always releases one electron. A beta particle goes 200 to 300 cm in the air. Sufficient shields are heavy clothing, aluminum, plastics, etc. Example: 614C => 714N + //e//-

¡ ** Gamma-Ray Emission ** ( γ) : high energy photon that carries out excess of energy from the nuclei (metastable nuclei). The nucleus ejects a gamma ray (proton and mass number of 0) normally as beta and alpha emission. This is the fastest emission and travels at the speed of light. It can be shielded by lead and concrete. ¡ Electron Capture (EC)- a type of radioactive decay that occurs when an inner-core electron is captured by a proton from the nucleus to form a neutron. The process is usually accompanied by the emission of x-rays. ¡ Positron Capture. The nucleus captures a positive electron so that a positron is part of the reactant side, resulting in an increase in the atomic number (increased number of protons) of the resulting new atom on the product side. The mass number stays the same. When positron emission occurs, a proton forms a positron and a neutron. Consequently, after positron emission, the radionuclide is going to become a different element that is one element lower in terms of atomic numbers. So, if astatine (atomic number 85) underwent positron emission for some reason, the daughter isotope would be polonium (atomic number 84). Although the atomic number changed, the mass number would stay the same because a neutron formed and this neutron is part of the nucleus.  Understand how radioactivity can be used for: ¡ Induce diseases : The chemical basis of radiation damage is that of ionizing radiation that can remove electrons from atoms and molecules in its path, leading to the formation of ions and radicals. Exposure to high-energy radiation can induce cancer. ¡ Detect diseases : Radioactive isotopes are used to trace the path of the atoms of an element in a chemical or biological process and are also used for diagnosis in medicine because they are easy to detect. Radioactive isotopes will tend to gather in higher concentrations where cells are being produced more rapidly ie: "cancer cells" ¡ Chemical study of matter :  Be able to write and balance nuclear equations balance it so that the number of neutrons and protons on each side of the equation are equal  Be able to predict the nuclear decay of an atom based on: ¡ Atom’s molar mass ¡ ** Atom’s proton/neutron ratio ** When the proton/neutron ratio is high (too many protons and not enough neutrons, assuming I remember from the book correctly and protons was on the x-axis, neutrons y-axis) and the isotope is below the 'safety belt' or w/e it's called (it's the graph that tells you the region where isotope stability is), the isotope is going to need to lose protons and gain neutrons to reach a stable nuclide combination. The emissions that allow the isotope to gain stability are positron emission and electron capture. Both of these emissions results in the loss of a proton and the gain of a neutron. For atoms with high atomic numbers, if there are increasingly more neutrons than protons then stability is favored, whereas with other atoms, stability is favored with a 1:1 ratio of neutrons:protons. As the mass increases, you need more neutrons than protons. ¡ Atom’s internal energy (stability)  Be able to calculate the following values for a atom: ¡ Mass defect: mass of an atom - (sum of protons,neutrons, and electrons) ¡ Binding energy: ∆E=(∆m)c² E = energy, m = mass, and c = velocity of light (2.99792458x10 ⁸ ) Be able to describe and explain the processes of nuclear fission : is a nuclear reaction is which the nucleas of an atom splits into smaller parts (lighter nuclei), often producing free neutrons and photons in the form of gamma rays.  Be able to use isotopic values (kinetic values) to solve problems involving radioactive dating.  Be able to calculate the following values for a radioactive decay: The half life for radionuclides are first order. So, the value of the half-life is dependent on the decay constant,k. The equation to determine the half-life is 0.693 divided by the decay constant. ¡ Rate constant : ln __[A]__t = -kt [A]o ¡ Initial and final concentration (or activity) of the radioactive material: ln(Nt/No)=-kt, another way to express the equation as taught in calculus A(f)=A(0)e^(-rt) (next few lines represent key) A(f)= Concentration final A(0)=Concentration initial, also called "A naught"has multiple applications as naught means literally "nothing" e= the constant "e" r= k as defined in Che 102 t= time elapsed
 * ¡ Positron Emission **
 * ¡ Half life (  λ) **