Nuclear Chemistry Nuclear Chemistry The study of reactions

Nuclear Chemistry

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 (a) • Helium nucleus • 2 protons & 2 neutrons • mass = 4 amu • charge = +2 • Penetration power: small

Beta Particle (b) • 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 (p) • 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 4 4 • Alpha: 2 He or 2 a 0 0 • Beta: -1 e or – 1 b 0 • Gamma: 0 0 • Positron: +1 e 0 • K-electron: -1 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 b emission of Pm-142 a emission of U-238 K-capture by O-15 p addition of O-18

Transmutation Rxns a emission of U 238 followed by two separate b emissions:

Transmutation Rxns a bombardment of Th-234 followed by two separate b emission:

Predict Products a Neutron absorption by U 238 followed by two separate b emission:

Predict Products a emission of O-18 followed by a b emission:

Predict Products K-capture by V-45 followed by neutron emission then a 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 = kd. X/dt ln(Xo/X) = kt 1/2 k = 0. 693/t 1/2 = half-life

1 st Order Age Dating Formula t = ln(X /X )t i f 1/2 0. 693

Calculate the age of a skeleton found with 0. 125 % C-14 when atmospheric C-14 = 1. 00 %. t 1/2 C-14 = 5720 yr

Calculate the age of a tooth found with 0. 00132 % C-14 when atmospheric C-14 = 1. 00 %. t 1/2 C-14 = 5720

Calculate the age of a bone found with 0. 000300 % C-14 when atmospheric C 14 = 1. 00 %. t 1/2 C-14 = 5720

Mass-Energy Relations DE = 2 Dmc

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: DE = 2 Dmc

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

In an atomic bomb, 40. 00 kg of U-235 (235. 401) is split into Ba-144 (14 3. 223) + 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