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 19th century Ernest Rutherford discovered that there were two types of radiation; alpha(𝞪) and beta(𝛃). Later on, Paul Villard discovered the gamma ray (𝜸).

Characteristics of 𝞪, 𝛃 & 𝜸 Name Symbols Charge Mass(g/particle) Alpha 2+ 6.65x10-24 Beta 1- 9.11x10-28 Gamma 𝞬

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 𝞫 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 & 126

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=mc2 or Δc2 ;c=speed of light=3x108 m/s △E=-4.54x10-12 -per nucleon:1.14 J/nucleon

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 sustain a chain reaction

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 1kg=6.022x1026 amu or 1g=6.022x1023 =1 mol/amu mass of products- mass of reactants Subatomic Particle Mass (kg) amu Neutron 1.67497x10-27 1.008665 Proton 1.67357x10-27 1.007825

Rate of Decay The negative change in the number of particles per unit of time -ΔN / Δt= kN ln(N/N0)=-kt N0 = # 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 t1/2=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 →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 (𝛃emitter): decays, 5730 half-life →carbon -12 is stable

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