4.3 NOTES Nuclear Radiation

IV. Unstable nuclei and radioactive decay A. Radioactivity The spontaneous emission of radiation which results in a change in an element’s identity. Discovery led to transuranium elements;  

B. Types of radiation 1. Alpha radiation: α; actually He atoms and represented 4He2; 2 protons and 2 neutrons; 2p+ are attracted to negatively charged plate;

  Sample Problems: Ra-226 decays by alpha emission 226 = mass number for this particular isotope and 88 is the atomic number of radium; write it as a nuclear symbol; Decay, emission, produces – all imply particles are on the right side of the arrow so the alpha particle (4He2) is placed to the right of the  –set up as an algebra equation with the arrow being the equal sign. Top numbers = top numbers, bottom numbers = bottom numbers. 226Ra88  4He2 + ??Xx?? ans: 222Rn86 top: 226 = 4 + x bottom: 88 = 2 + x

2. Beta radiation: β; emission of high speed e- with a -1 charge; 0e-1; deflected toward the positively charged plate; formed when a neutron decomposed into a proton (which stays in the nucleus) and an e- which is emitted from the nucleus

Example: C-14 decays be beta emission 14C6  0e-1 + 14N7

3. Gamma radiation: high energy radiation w/ no electrical charge and no mass; not deflected by electric or magnetic fields; account for most of the energy lost in a nuclear reaction; Example: U-238 decays by emitting an alpha particle and 2 gamma rays 238U92  4He2 + ɣ + 234Th90

4. Other particles: neutrons can also be emitted; 1n0   5. Nuclear stability – atomic stability is determined by the proton to neutron ratio; atoms with too many or too few neutrons are unstable; unstable nuclei will lose energy (in the form of radiation) to become more stable

Sample Problem: U-235 is bombarded with a neutron Sample Problem: U-235 is bombarded with a neutron. A proton is produced as well as another element. What is the other element? Bombarded, collided, struck – all imply particles are on the left side of the arrow.   235 U92 + 1n0  1p1 + ans: 235Pa91