Nuclear Chemistry The study of nuclear reactions and

Nuclear Chemistry The study of nuclear reactions and their uses By: Robyn Louis & Alyssa Williams

Discovery of Radioactivity ✘Henri Becquerel discovered radioactivity ✘In the late 19 th century Ernest Rutherford discovered that there were two types of radiation; alpha(��) and beta(��). Later on, Paul Villard discovered the gamma ray (��).

Characteristics of �� , �� & �� Name Charge Mass(g/particle) Alpha 2+ 6. 65 x 10 -24 Beta 1 - 9. 11 x 10 -28 0 0 Gamma Symbols ��

Radioactivity ✘gamma rays are a form of electromagnetic radiation and is the most penetrating allowing it to absorb the most energy , then beta and lastly alpha ✘radiation energy transferred to any material to be absorbed meaning that energy is being absorbed

Nuclear Reactions and Radioactive Decay ✘Radioactivity is the result of a natural change of an isotope from one element to another ✘alpha particle emissions causes a decrease of two units in atomic number and four units in mass number ✘beta particle emissions cause no change in atomic number and an increase of one unit in mass number ✘gamma rays cause no change

Radioactive Decay ✘ radioactive isotopes decay in order to form a radioactive product which causes several nuclear reactions which is ended by a nonradioactive isotope ✘ positron emission: a particle with the same mass as an electron but with the opposite sign. ✘ electron capture : nucleus captures an electron from the electron cloud surrounding the nucleus(same mass, atomic number reduced by 1)

Continued. . . ✘ Too many neutrons = spontaneous �� production ✘ Too many protons= spontaneous positron production ✘ When a nuclide has ≥ 84 protons it tends to undergo radioactive decay ✘ Nuclides with odd protons or neutrons are more likely to undergo radioactive decay ✘ Proton/neutron numbers 2, 8, 20, 28, 50, 82

Nuclear Binding Energy (Eb) ✘Einstein determined that matter is energy and that rest energy is the amount of energy with in a piece of matter; mass is a form of energy ✘the measure of energy to seperate the nucleus of an atom into protons and neutrons ✘E=mc 2 or Δc 2 ; c=speed of light=3 x 108 m/s △E=-4. 54 x 10 -12

Continued. . . ✘The larger the bind, the more stable the nuclei is ✘Higher the bind the more mass is turned into energy to bind the nucleons together

Fission ✘fission: splitting a heavy nuclei into 2 smaler nuclei with smaller mass numbers →mass of product ＜ mass of reactants (missing mass = energy) ✘Material that starts reaction is the product and can start another reaction ✘Minimum amount of nuclide that provides the number of neutrons to

Fusion ✘Combining two light nuclei to form a heavier , more stable nucleus ✘energy from H bomb

Mass Defect (mass converted into binding energy) ✘difference between mass of an atom and the sum of its protons, neutrons and electrons Subatomic Particle Mass (kg) amu Neutron 1. 67497 x 10 -27 1. 008665 Proton 1. 67357 x 10 ✘ 1 kg=6. 022 x 1026 amu -27 1. 007825 or 1 g=6. 022 x 1023 =1 mol/amu ✘mass of products- mass of reactants

Rate of Decay ✘The negative change in the number of particles per unit of time ✘-ΔN / Δt= k. N ✘ln(N/N 0)=-kt ✗N 0 = # of nuclide t t=0 ✗N=# of nuclide remaining at time of t

Half Life Time required for the # of nuclides to reach half the original value ✘t 1/2=ln(2)/k=. 693/k

Nuclear Transmutations ✘The change of one element into another by changing the protons -cyclotron: particle is accelerated from inside to outside through a spiral path -linear accelerator: particle is accelerated down a linear track -Transuranium elements: elements that have been synthesized by nuclear transformations after Ur ( 93 -112, 114, 116, 118)

Detection/ Use of Radioactivity ✘Detection →geiger counter: Argon becomes ionized and when struck by a high energy particle electrical energy is amplified and radioactivity intensity is shown →scintillation counter: zinc sulfide give off light when struck by high energy particle from radioactive decay

Continued. . . ✘Dating →decay rate of unstable nuclides used to determine age →carbon-14 (��emitter): decays, 5730 half-life →carbon -12 is stable

ASSIGNMENT Pg. 1091 -12 Pg. 1092 -18, 22, 30 Pg. 1093 -46 Pg. 1094 -52