Nuclear Reaction Lecture PDF

NUCLEAR REACTIONS Prepared By Engr. Rosalina M. Corpuz School of Engineering and Architecture Nuclear Reactions Nuclear Reactions  The Structure of Atom Two Kinds of Particles 1. Nucleus – the atom’s central core, which is positively charged and...

NUCLEAR REACTIONS Prepared By Engr. Rosalina M. Corpuz School of Engineering and Architecture Nuclear Reactions Nuclear Reactions  The Structure of Atom Two Kinds of Particles 1. Nucleus – the atom’s central core, which is positively charged and contains most of the atom’s mass. 2. Electron – is a very light negatively charged particle that exists around the atom’s positively charged nucleus Nuclear Reactions Discovery of Electron J.J. Thompson British Physicist J.J. Thompson's most significant discovery about the atom was the identification of the electron in 1897. Through his famous cathode ray tube experiment, Thomson demonstrated that atoms were not indivisible as previously believed, but instead contained smaller, negatively charged particles and named it as electron. Nuclear Reactions  Mass of Electron Robert Millikan US Physicist 1909, performed a series of experiments about the charge and mass of the electron using the Millikan Oil Drop Experiment electrons are particles found in all atoms cathode rays are streams of electrons the electron has a charge of -1.60 x 1019 C the electron has a mass of 9.1 x 10-28 g Nuclear Reactions  A New Theory of the Atom since the atom is no longer indivisible, Thompson must propose a new model of the atom to replace the first statement in Dalton’s Atomic Theory Thompson proposes that instead of being a hard, marble-like unbreakable sphere, the way Dalton described it, that it has an inner structure. Nuclear Reactions  Radioactivity in the late 1800s, Henri Becquerel and Marie Curie discovered that certain elements would constantly emit small, energetic particles and rays these energetic particles could penetrate matter Ernest Rutherford discovered that there were three different kinds of emissions alpha, a, particles with a mass 4x H atom and + charge beta, b, particles with a mass ~1/2000th H atom and – charge gamma, g, rays that are energy rays, not particles Nuclear Reactions Nuclear Model of the Atom According to Rutherford’s model, most of the mass of the atom is concentrated in a positively charged center called nucleus, around which the negatively charged electrons move. Structure of Nucleus Rutherford proposed that the nucleus had a particle that had the same amount of charge as an electron but opposite sign based on measurements of the nuclear charge of the elements this particle is called proton charge = +1.602 x 10 -19 C mass = 1.67262 x 10 -27 g since protons and electrons have the same amount of charge, for the atom to be neutral there must be equal numbers of protons and electrons Nuclear Reactions utron – is a nuclear particle having a mass almost identical to that of the proton but no electrical charge Particle Mass ( Kg) Charge (C) Charge(e) Electron 9.109 x 10 -31 - 1.602 x 10 -19 - 1 Proton 1.67262 x 10 -27 + 1.602 x 10 -19 +1 mic Number (Z) – is the Neutron number 1.7493 x 10of -27protons in the nucleus of an atom. 0 0 ss Number (A) – is the total number of protons and neutrons in the nucleus. clide – is a particular nucleus characterized by a definite atomic number and mass number Nuclear Reactions Nuclear Reactions Nuclear Radiation Radioactivity - the process by which an unstable nucleus emits one or more particles or energy in the form of electromagnetic radiation. (it just wants to become stable) Nuclear decay Isotopes - same of numbers of protons but different number of neutrons. Nuclear Radiation - the particles that are released from the nucleus during radioactive decay. Do not confuse this with light radiation. Can be very harmful to the materials that absorb the radiation. When a radioactive nucleus decays, the nuclear radiation leaves the nucleus. Nuclear Reactions Type of Radiation Nuclear Reactions Alpha particles (+) - consist of protons and neutrons. Uranium is a radioactive element that occurs in 3 isotope forms. Energy source in nuclear power plants. U234, U235, U238 Responsible for most of the heat in Earth’s core. U238 undergoes nuclear decay by emitting positively charged particles (Rutherford) Alpha particles - positively charged atom that is released in the disintegration of radioactive elements and that consists of two protons and two neutrons. So massive they barely travel through a piece of paper. Pull electrons from other matter, thus losing energy as it passing through. Nuclear Reactions  0 Beta particles (-) 𝑒 −1 Travels through matter that alpha particles do not. Only released during certain types of radioactive decay. Fast moving When neutrons decay, they form a proton and electron. Electron has little mass and is ejected from nucleus at high speed Easily go through paper but stopped by aluminum or wood. Like alpha particles, they ionize atoms which slows them down. Nuclear Reactions Gamma rays are very high energy More penetrating than beta particles Gamma ray is the high-energy photon emitted by a nucleus during fission and radioactive decay. Unlike beta and alpha, they are not made of matter. Photons Have more energy than light or X-rays Pose highest danger to health Nuclear Reactions Neutron radioactivity may occur in an unstable nucleus Neutron are not charged, therefore do not ionize matter. Can travel the furthest of all three previously mentioned forms of radioactivity. Nuclear Reactions Nuclear Reactions Nuclear Decay Nuclear Equation – shows the radioactive decomposition of an element 6C → 7N + e 14 14 0 -1 Nuclear Forces – strong nuclear force holds neutrons and protons together to form a nucleus (counters electromagnetic repulsion). Weak nuclear force operates within individual nucleons and gives rise to some kinds of radioactivity Nuclear Reactions Nuclear Reactions Types of Radioactive Decay Alpha-particle Production Alpha particle – helium nucleus – Examples Net effect is loss of 4 in mass number and loss of 2 in atomic number. Nuclear Reactions Nuclear Reactions Beta-particle Production Beta particle – electron – Examples Net effect is to change a neutron to a proton. Nuclear Reactions Nuclear Reactions Gamma Ray Release Gamma ray – electromagnetic radiation – Examples Net effect is no change in mass number or atomic number. Nuclear Reactions Positron Production Positron – particle with same mass as an electron but with a positive charge (antimatter version of an electron) – Examples Net effect is to change a proton to a neutron. Nuclear Reactions Write the nuclear reaction for position decay of 35 75 Re Write the nuclear reaction for position decay of 8 5 B Nuclear Reactions Electron capture Electron capture - inner orbital electron is captured. New nucleus formed. Neutrino and gamma ray produced Net effect is to change a proton to a neutron Nuclear Reactions Write the nuclear reaction for electron capture decay of 38 18 Ar Write the nuclear reaction for electron capture decay of 125 53 I Nuclear Reactions 1. Write the nuclear reaction for alpha decay of 38 18 Ar. 2. Write the nuclear reaction for beta decay of 150 64 Gd. 3. Write the nuclear reaction for positron decay of 45 22 Ti 4. Write the nuclear reaction for electron capture decay of 247 99 Es Nuclear Reactions Nuclear Reactions