Nuclear Chemistry

The study of reactions that take place in the nucleii of atoms

Chemical Reactions In normal chemical reactions, only the electrons are involved

Radioactive Nucleii A nucleus that spontaneously decomposes

Isotopes Elements with the same atomic number, but different mass number

Isotopes Elements with = numbers of protons, but  numbers of neutrons

Isotopes All elements have at least one radioactive isotope

Radiation The emission of particles & rays from spontaneously decomposing nucleii

Modes of Decay Alpha emission Beta emission Gamma emission Positron emission K-electron capture

Alpha Particle (  ) Helium nucleus 2 protons & 2 neutrons mass = 4 amu charge = +2 Penetration power: small

Beta Particle (  ) High speed electron 1 electron mass = 1/1836 amu charge = -1 Penetration power: medium

Gamma Ray (  ) High energy photon Electromagnetic wave mass = 0 charge = 0 Penetration power: great

Positron (  ) Positive electron 1 positive electron mass = 1/1836 amu charge = +1 Penetration power: medium

K-capture The capture of an inner level e - by the nucleus 1 electron mass = 1/1836 amu charge = -1

Nuclear Symbol Alpha: 2 4 He or 2 4  Beta: -1 0 e or –1 0  Gamma: 0 0  Positron: +1 0 e K-electron: -1 0 e

Fission The splitting of a nucleus into smaller nucleii involving the release of energy

Fusion The combining of smaller nuclei into a larger one involving the release of energy

Transmutation Rxns Nuclear reactions in which one element is changed into another

Transmutation Rxns Reactions in which the nucleus of an atom is changed

Transmutation Rxns Both fission & fusion are examples of transmutation rxns

Transmutation Rxns Can occur through emission of or bombardment by radioactive particles

Transmutation Rxns  emission of Pm-142  emission of U-238 K-capture by O-15  addition of O-18

Transmutation Rxns  emission of  U   followed by two separate  emissions:

Transmutation Rxns  bombardment of Th  followed by two separate  emission:

Predict Products a Neutron absorption by U   followed by two separate  emission:

Predict Products  emission of O-18 followed by a  emission:

Predict Products K-capture by V-45 followed by neutron emission then  emission

Decay Rate The rate at which a radioactive nucleus breaks down

Half-Life The time it takes for 50 % of the radioactive nucleii to decompose

Decay Rate Rate = kdX/dt ln(X o /X) = kt 1/2 k = 0.693/t 1/2 t 1/2 = half-life

1st Order Age Dating Formula t = ln(X i /X f )t 1/

Calculate the age of a skeleton found with % C-14 when atmospheric C-14 = 1.00 %. t 1/2 C-14 = 5720 yr

Calculate the age of a tooth found with % C-14 when atmospheric C-14 = 1.00 %. t 1/2 C-14 = 5720

Calculate the age of a bone found with % C-14 when atmospheric C- 14 = 1.00 %. t 1/2 C-14 = 5720

Mass-Energy Relations  E =  mc 2

Nuclear Fact The mass of any nuclei is different than the sum of the masses of its protons & neutrons

Nuclear Fact The energy corresponding to the mass difference can be solved using:  E =  mc 2

Binding Energy The energy that holds a nucleus together which corresponds to  m of nucleus

In an atomic bomb, kg of U-235 ( ) is split into Ba-144 ( ) + Kr-89 (89.335) + 2 neutrons (1.014). A) Calculate the energy released. B) Calculate the wavelength of the  ray

Show neutron bombardment of Ra-223 followed by 3 alpha emissions