nuclear transmutations - changing the atom’s identity  

• 1st conversion done by Rutherford
• nuclear reactions can start by striking nuclei w/ particles
• particle accelerators - slams charged particles against nuclei
  • needs high speed to overcome electrostatic repulsion between particles and nuclei
  • not used for neutrons (not repelled by nuclei)
• transuranium elements - elements w/ atomic number greater than 92

Xenon-118 undergoes electron capture to become what?  

• atomic number decreases by 1
• atomic mass stays the same
• 118Xe + -1e0 >> 118I

Carbon-14 undergoes betay decay to produce what?  

• atomic number increases by 1
• atomic mass stays the same
• 14C >> 14N + -1e0

radioactive decay rates - 1st-order kinetic process

• half-life - time required for 1/2 of given quantity to react
• k = 0.693 / t1/2
• ln (Nt / N0) = -kt

An old piece of wood has carbon-14 activity of 11.7 disintegrations per minute per gram. Current carbon-14 activity is 15.3 disintegrations per minute per gram. The half-life of carbon-14 is 5714 years. How old is that old piece of wood?  

• Given:
  • t1/2 = 5714
  • Nt = 11.7
  • N0 = 15.3
• k = 0.693 / 5714 = 1.2 x 10-4
• ln (11.7 / 15.3) = -(1.2 x 10-4)t
• t = 2212 years old