Nuclear Decay

Radioactivity The emission of high-energy radiation or particles from the nucleus of a radioactive atom.

3 Types of Radiation Alpha Radiation Beta Radiation Gamma Radiation

Alpha Radiation Radiation in the form of alpha particles What are alpha particles? –Particles that consist of 2 protons and 2 neutrons with an atomic mass of 4 Alpha particles have an atomic mass of 4 and an atomic number of 2 –Why an atomic number of 2?

Problems with Alpha Particles Alpha particles can burn your skin however they can also be stopped by a piece of paper

Beta Radiation Radiation given off as beta particles –What are beta particles? Particles consisting of: –An electron emitted from a decaying neutron in the nucleus –Does not have an atomic mass –Atomic number of -1

Problems with Beta Particles 100 time greater penetrating ability than alpha particles –Can penetrate through 3 mm of aluminum

Gamma Rays Electromagnetic wave (study this more when we cover physics) Carry a lot of energy Atomic Mass of 0 No atomic number

Problems With Gamma Rays Carry a lot of energy Most penetrating of the three types of radiation –Pass through several cm of lead

Radioactive Decay Are radioactive elements stable? No Radioactive Decay is the process by which atomic nuclei emit particles or rays to become lighter and more stable –3 types of decay Alpha Decay Beta Decay Gamma Decay

Alpha Decay Step 1. A nucleus releases an alpha particle (2 neutrons and 2 protons) decreasing the mass number of the nucleus What does that mean? –The original atom is no longer the same –The atomic number is decreased by 2 Why? –Because the atomic number is based on the # of protons, and now the # of protons is different by 2

Alpha Decay

Beta Decay A neutron inside a nucleus spontaneously decays producing a proton and electron A beta particle in the form of an electron is released from the nucleus Because a proton is produced, so is a new atom. The atomic number of the original atom is increased by one However the mass number does not change –Carbon 14 (6 protons and 8 neutrons) –Nitrogen 14 (7 protons and 7 neutrons)

Beta Decay

Gamma Decay When gamma rays are emitted by a nucleus the nucleus does not change into a different nucleus However, since the gamma ray is an extremely high-energy wave the nucleus makes a transition to a lower energy state

Gamma Decay

Half-Life What is a half-life? –The fixed rate of decay of a radioactive element in which the element will decay into another element. –The half life of carbon 14 is 5730 years In 5730 years the isotope has decayed by 50% –Left with 50% C-14 and 50% N-14 In another 5730 years the isotope has decayed by another 50% –From 50% to 25% »Left with 25% C-14 and 75% N-14