Known nuclides

PROPERTIES OF FUNDAMENTAL PARTICLES Particle Symbol Charge Mass (x Coulombs) (x kg) Proton P Neutron N Electron e

NUCLEAR STABILITY Modes of Radioactive Decay Alpha Decay - Heavy Isotopes He +2 -  Beta Decay - Neutron Rich Isotopes - e - -   Positron Emission -Proton Rich Isotopes -   Electron Capture - Proton Rich Isotopes x - rays Gamma-ray emission(  - Decay of nuclear excited states Spontaneous Fission - Very Heavy Isotopes

Alpha Decay -Heavy Elements 238 U 234 Th +  + E T 1/ 2 = 4.48 x 10 9 yrs 210 Po 206 Pb +  + E T 1/ 2 = 138 days 256 Rf 252 No +  + E T 1/ 2 = 7 msec 241 Am 237 Np +  + E T 1/ 2 = 433 days

Beta Decay - Electron Emission N P + +   + Energy 90 Sr 90 Y +   + Energy T 1/ 2 = 30 yrs 14 C 14 N +   + Energy T 1/ 2 = 5730 yrs 247 Am 247 Cm +   + Energy T 1/ 2 = 22 min 131 I 131 Xe +   + Energy T 1/ 2 = 8 days

Natural Decay Series of Existing Isotopes 40 K 40 Ar T 1/2 = 1.29 x 10 9 yrs 232 Th 208 Pb T 1/2 = 1.4 x yrs 235 U 207 Pb T 1/2 = 7 x 10 8 yrs 238 U 206 Pb T 1/2 = 4.5 x 10 9 yrs

Figure 21.2: Decay series

Natural Decay series for Uranium U 234 Th 234 Pa 234 U 230 Th 226 Ra 222 Rn 218 Po 214 Pb 218 At 214 Bi 210 Tl 214 Po 210 Pb 206 Hg =  decay 210 Bi 206 Tl =   decay 210 Po 206 Pb 238 U -- 8  decays and 6  decays leaves you with Pb

The decay of a g sample of strontium-90 over time.

Accelerator tunnel at Fermilab, a high- energy particle accelerator in Batavia, Illinois. Source: Fermilab Batavia, IL

Plot of energy versus the separation distance

Units used for Nuclear Energy Calculations electron volt - (ev) The energy an electron acquires when it moves through a potential difference of one volt: 1 ev = 1.6 x J Binding energies are commonly expressed in units of megaelectron volts (Mev) 1 Mev = 10 6 ev = 1.6 x J A particularly useful factor converts a given mass defect in atomic mass units to its energy equivalent in electron volts: 1 amu = 931 x 10 6 ev = 931 Mev

Binding energy per nucleon as a function of mass number.

Binding Energy per Nucleon of Deuterium Deuterium has a mass of amu. Hydrogen atom = 1 x amu = amu Neutrons = 1 x amu = amu amu Mass difference = Theoretical mass - actual mass = amu amu = amu Calculating the binding energy per nucleon: Binding Energy amu x Mev / amu Nucleon 2 nucleons = =

Calculation of the Binding Energy per Nucleon for Iron- 56 The mass of Iron -56 is amu, it contains 26 protons and 30 Neutrons Theoretical Mass of Fe - 56 : Hydrogen atom mass = 26 x amu = amu Neutron mass = 30 x amu = amu amu Mass defect =Actual mass - Theoretical mass: amu amu = amu Calculating the binding energy per nucleon: Binding Energy amu x Mev / amu nucleon 56 nucleons = =

Calculation of the Binding Energy per Nucleon for Uranium The actual mass of Uranium = amu, and it has 92 protons and 146 neutrons Theoretical mass of Uranium 238: Hydrogen atom mass = 92 x amu = amu neutron mass = 146 x amu = amu amu Mass defect = Actual mass - Theoretical mass: amu amu = amu Calculating the Binding Energy per nucleon: Binding Energy amu x Mev / amu mucleon 238 nucleons = =

Oppenheimer

Both fission and fusion produce more stable nuclides and are thus exothermic.

Upon capturing a neutron, the 235 U nucleus undergoes fission to produce two lighter nuclides, free neutrons (typically three), and a large amount of energy.

Representation of a fission process in which each event produces two neutrons, which can go on to split other nuclei, leading to a self-sustaining chain reaction.

If the mass of the fissionable material is too small, most of the neutrons escape before causing another fission event; thus the process dies out.

Nuclear power plant

Breeder reactor at a nuclear power plant in St. Laurent-Des Eaux, France. Source: Stock Boston

A Uranium "button" for use as a fuel in a nuclear reactor.

Schematic of a reactor core