Chapter 28 Notes, part I

1
Chapter 28 Notes, part I

• Nuclear Reactions a, b, g Decay

2
Radiation and Radioactivity

• Radioactivity was discovered by Henri Becquerel
  in 1896.
• It is the spontaneous emission of particles or
  energy by unstable atomic nuclei.
• The emitted particles are called radiation, and
  the change in nucleus that results is called
  radioactive decay.

3
Radiation

• There are three types of radiation we will
  discuss, alpha (a), beta (b) and gamma (g)
  particles.
• Alpha particles have the least amount of energy,
  while gamma particles have the most.

4
1) Alpha Decay

• Alpha decay occurs when unstable isotopes try to
  stabilize by emitting an alpha particle.
• An alpha particle is made of two protons and two
  neutrons, and its symbol is a or He.
• Ra a

42
42
23688
42
23286
He Rn
5
2) Beta Decay

• There are three types of beta decay beta
  emission, positron emission and electron capture.
• A beta particle is the same thing as an electron
  with a symbol of b or e-.
• Beta emission looks like
• C a e- N

0 -1
0 -1
146
147
0 -1
6
Electron Capture and Positron

• Electron capture occurs when instead of emitting
  an electron, one is pulled into the nucleus.
• Au e- a Pt
• A positron is an odd particle it is an electron
  with a positive charge!
• Sb a e- Sn

19579
19578
0 -1
11651
0 1
11650
7
3) Gamma Radiation

• Frequently a or b decay produces energy, which is
  released as gamma rays (g).
• In most cases, it is only given off when other
  types of radiation occur, and since it has no
  particles, its symbol is just g.

8
Why does radioactive decay occur?

• All stable isotopes of an atom lay inside what is
  called the band of stability.
• This is a ratio of protons to neutrons that is
  inherently stable.
• Atoms not in this band will undergo radioactive
  decay to do so.

9
Predicting how an isotope will decay

• An isotope is just too big
• a decay
• An isotope has too many neutrons
• b decay
• An isotope has too few neutrons
• e- capture, positron emission

10
Write the Nuclear Reaction for

• The a decay of Americum-245
• The b decay of Thorium-236
• The electron capture of Iodine-125
• The positron emission of Potassium-40