Nuclear Chemistry

Alpha Decay (⍺) -zxA → 24He +z-2x-4B 

  • Parent Isotope (A) splits into daughter isotope (B) and Helium 

  • Daughter isotope is a different element (2 places back on the periodic table)

  • Not penetrating because of He (captures electrons mid-travel)

  • Damaging because d particles knock atoms of molecules

  • Common in elements > 83

  • Symbol: 24=24He 

Beta decay () -zxA → -10e-1+z+1xB 

  • Parent isotope (A) gains a proton ← daughter isotope (B) w/ same mass bc 1 neutron took from daughter isotope

  • Penetrating bc smaller particles but electrostatic forces eventually stop them

  • Common in elements w high neutron to proton ratio

  • Symbol: -10=-10e 

Gamma decay () -zxA → 00+zxB 

  • Parent isotope (A) is excited but falls to lower energy state in daughter isotope (B)

  • Most penetrating radiation

  • Photons pass through body and damage ionizing all molecules in the way

  • Symbol: 00=photon

Positron emission (beta positive decay) (+) -zxA → 10e+z-1xB 

  • A positron is emitted from parent isotope (A) to create daughter isotope (B)

  • Positron is like an electron (mass + charge force) but positive charge

  • Proton breaks into neutron w/ mass and neutral charge and positron w/ no mass & positive charge

  • Common in lighter elements w/ low neutron to proton ratio

  • Symbol: 10=10e 

Electron capture (EC) -zxA +-10e→z-1xB 

  • Parent isotope (A) loses electrons to form daughter isotope (B)

  • Nucleus captures 1 inner shell electron which reduces atomic number

  • Captured electron forms proton with neutron

  • Common in larger elements w/ low neutron to proton ratio

Amount vs. Time Graphs

  • Exponential decay curve

  • Represents characteristic decay of radioactive isotopes w/ constant half-life

Decay series (A vs. Z graph)

  • Alpha decay (goes down diagonally) loses to protons and 2 neutrons 

  • Beta decay (goes to the right) gains 1 proton while losing 1 electron as nucleus moves toward stability


Nuclear fusion vs. fission

  • Involves either combining or splitting the nuclei of atoms

  • Energy is released for both and formed nuclei is stable

  • Fusion: small nuclei combine to form larger nucleus (stars)

  • 12H+13H=24He+01n → n = neutron

  • Fission: large nucleus splits into smaller nuclei (power plant) 

  • 01n+92235U=92236U*

  • 01n+92235U=92236U* --Z1A1X1+Z2A2X2+N01n

  • quick energy release

Half-Life

  • Time for half of original isotope to radioactive decay to daughter isotopes

  • Short half-life (i.e. Radon) more dangerous because more radiation in short amount of time

Formulas

  • N (final amount)=N0(initial amount)(½)t (time)t (1/2)

  • ln (N/N0)=-k(rate of decay)t

  • t1/2=0.693k