THE NUCLEUS: A CHEMIST’S VIEW

Nuclear Symbols Element symbol Mass number, A (p + + n o ) Atomic number, Z (number of p + )

Balancing Nuclear Equations Σ A reactants = Σ A products Σ Z reactants = Σ Z products = (1) = (0)

Balancing Nuclear Equations #2 226 = 4 + ____ = 2 + ___ 86 Atomic number 86 is radon, Rn Rn

Balancing Nuclear Equations # = (1) + ____ = (0) + ____ Atomic number 39 is yttrium, Y Y

Alpha Decay Alpha production (a): an alpha particle is a helium nucleus Alpha decay is limited to heavy, radioactive nuclei

Alpha Radiation Limited to VERY large nucleii.

Beta Decay Beta production (  ): A beta particle is an electron ejected from the nucleus Beta emission converts a neutron to a proton

Beta Radiation Converts a neutron into a proton.

Gamma Ray Production Gamma ray production (  ): Gamma rays are high energy photons produced in association with other forms of decay. Gamma rays are massless and do not, by themselves, change the nucleus

Positron Production Positron emission: Positrons are the anti- particle of the electron Positron emission converts a proton to a neutron

Electron Capture Electron capture: inner-orbital electron is captured by the nucleus Electron capture converts a proton to a neutron

Nuclear Stability Decay will occur in such a way as to return a nucleus to the band (line) of stability. The most stable nuclide is Iron-56 If Z > 83, the nuclide is radioactive

Half-life Concept

Decay Kinetics Decay occurs by first order kinetics (the rate of decay is proportional to the number of nuclides present) N = number of nuclides remaining at time t N 0 = number of nuclides present initially k = rate constant t = elapsed time

Calculating Half-life t 1/2 = Half-life (units dependent on rate constant, k)

Sample Half-Lives

Nuclear Fission and Fusion Fusion: Combining two light nuclei to form a heavier, more stable nucleus. Fission: Splitting a heavy nucleus into two nuclei with smaller mass numbers.

Fission

Fusion

Energy and Mass Nuclear changes occur with small but measurable losses of mass. The lost mass is called the mass defect, and is converted to energy according to Einstein’s equation: Δ E = mc 2  m = mass defect  Δ E = change in energy c = speed of light Because c 2 is so large, even small amounts of mass are converted to enormous amount of energy.