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Nuclear Chemistry-II (JAMB (UTME)) Presented by Saheed Adewale Lateef [B.Eng. (ChE)]
Learning Outcomes After this class, it is expected that students are able to differentiate between nuclear and chemical reactions; artificial and natural radioactivity Students should define and explain what nuclear fission and fusion are and identify there areas of applications How to balance them. nuclear reactions should be understood by
Nuclear Reaction vs Chemical Reaction Nuclear reaction takes place in the atom s nucleus, the electrons in the atom are responsible for Chemical reactions. The chemical reactions involve the transfer, loss, gain and sharing of electrons and nothing takes place in the nucleus. Nuclear reactions involve the decomposition of the nucleus and have nothing to do with the electrons. In a nuclear reaction, the protons and neutrons react inside the nucleus and in chemical reactions the electrons react outside the nucleus. When comparing the energies, a chemical reaction involves only low energy change, where as a nuclear reaction has a very high-energy change.
In nuclear reaction, isotopes react differently while in chemical reaction, isotopes react the same way While the elements get transmuted into other elements in a nuclear reaction, the number of atom remains same with chemical reactions. When mass changes can be detected in a nuclear reaction, in the chemical reactions, the mass of the reactants are equal to mass of the products.
Natural and Artificial Radioactivity Nuclear reactions which occur spontaneously are said to be an example of natural radioactivity. There are three naturally occurring radioactive series among the elements in the periodic table. These are known as the uranium series, the actinium series and the thorium series, each named after the element at which the series start (except the actinium series which starts with a different uranium isotope). Each series decays through a number of unstable nuclei by means of alpha and beta emission, until each series end on a different stable isotope of lead.
Natural and Artificial Radioactivity (cont d) Not all nuclear reactions are spontaneous. These reactions occur when stable isotopes are bombarded with particles such as neutrons. This method of inducing a nuclear reaction to proceed is termed artificial radioactivity. This meant new nuclear reactions, which wouldn't have been viewed spontaneously, could now be observed. Since about 1940, a set of new elements with atomic numbers over 92 have been artificially made. They are called the transuranium elements.
Artificial Transmutation When one element is converted into another element artificially then it is known as Artificial Transmutation. It is a type of artificial radioactivity. Examples; Consider the Rutherford and below; Chadwick equations written 7 N 14 + 2 He 4 8O 17 + 1 H 1 4 Be 9 + 2 He 4 6C 12 + o n 1
Nuclear Fission Nuclear fission is a process where the nucleus of an atom is split into two or more smaller nuclei, known as fission products. The fission of heavy elements is an exothermic reaction and huge amounts of energy are released in the process. This energy can be used to produce nuclear power or to make nuclear weapons when we have fission chain reactions. Examples: in the manufacture of atomic bomb (uncontrolled reactions), electrical energy (controlled reactions) where Uranium-235 and Plutonium-239 are used.
Nuclear Fusion Nuclear fusion is the joining together of the nuclei of two atoms to form a heavier nucleus. If the atoms involved are small, this process is accompanied by the release of energy. It is the nuclear fusion of elements that causes stars to shine and hydrogen bombs to explode. As with nuclear fission then, there are both positive and negative uses of nuclear fusion.
Measurement of Radiation There are many instruments to measure radioactivity and each depends on some properties which include detection accuracy, cost, robustness. Below are the list of few instruments used to detect and measure radioactivity; Geiger-Muller counter Scintillation counter End-window G-M detector etc
Review There are two forces between the particles of the nucleus. The strong nuclear force (attraction between the nucleons) and the electromagnetic force (repulsion between like-charged protons). In atoms with large nuclei, the electromagnetic force becomes greater than the nuclear force and particles or energy may be released from the nucleus. Radioactive decay occurs when an unstable atomic nucleus loses energy by emitting particles or electromagnetic waves. The particles and energy released are called radiation and the atom is said to be radioactive. Radioactive isotopes are called radioisotopes. Radioactivity was first discovered by Marie Curie and her husband Pierre.
There are three types of radiation from radioactive decay: alpha (α), beta (β) and gamma (γ) radiation. During alpha decay, an alpha particle is released and consists of two protons and two neutrons bound together with low penetration power.. For beta decay, a beta particle is released where, a neutron is converted to a proton, an electron and a neutrino. A beta particle is the electron that is released. It has greater penetration power than alpha radiation. Gamma decay however, electromagnetic energy is released as gamma rays. Gamma radiation has the highest penetration power of the three radiation types. There are many sources of radiation. Some of natural and others are manmade.
Review (cont d) The half-life of an element is the time it takes for half the atoms of a radioisotope to decay into other atoms. Radiation can be very damaging. Some of the negative impacts of radiation exposure include damage to cells, genetic abnormalities and cancer. However, radiation can also have many positive uses. These include use in the medical field (e.g. chemical tracers), biochemistry and genetics, use in food preservation, the environment and in archaeology. Nuclear fission is the splitting of an atomic nucleus into smaller fission products. Nuclear fission produces large amounts of energy, which can be used to produce nuclear power, and to make nuclear weapons. Nuclear fusion is the joining together of the nuclei of two atoms to form a heavier nucleus. In stars, fusion reactions involve the joining of hydrogen atoms to form helium atoms.
Class Exercise JAMB2001, TYPE R, Q6 Gamma rays are used in medical treatment of diseases. Ans: Option D JAMB2013, TYPE U, Q6 Cobalt-60 finds application in radiography. Ans: Option A JAMB2000, Q12 Half-life indicates the time the element splits into two. Ans: Option C
Class Exercise JAMB 2002, TYPE K Q21 Beta emission is characterized by increase in atomic number of the new atom (+1) while the mass number is unchanged Ans: Option B Option C J2005, TYPE 4, Q34
Homework JAMB 2004, 40, R On emission of alpha particle, the mass number of the tom reduces by 4, hence 226= x+4 X = 222 Ans: Option D JAMB 2008, Q11 Bombarding an atom with either a neutron or proton is called artificial transmutation. Ans: Option C JAMB 2010, TYPE A, Q11 This is a combination of lighter atoms to form heavier atoms with the release of energy. Ans: Option C
Next video will be on Kinetic theory and Gas laws with sample Questions and Solutions
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