Nuclear RadiationHalf-Life

What is Radiation?

• Penetrating rays and particles emitted by a radioactive source

• Result of a nuclear reaction!– Involves the

changing of the atoms nuclei

Radioisotopes

• Isotopes– Elements with the

same # of protons & electrons, but a different # of neutrons!

• Radioisotopes– Unstable isotopes– In nuclear rxns their

nuclei undergo changes to become stable

Chemical vs. Nuclear rxns

Chemical Rxns

• Involve the transfer or sharing of e-

• Nuclei are unchanged

• Affected by ∆ in temp, pressure & catalyst

Nuclear Rxns

• Nuclei are changed to become stable

• Involve large amounts of energy being emitted

• Not affected by anything & cannot be stopped

Nuclear Stability

• Depends on the ratio of neutrons to protons in the nucleus & the overall size of the nucleus

• Too many or too few neutrons makes the nucleus unstable

• Unstable nucleus releases energy by emitting radiation during radioactive decay!

Types of Radiation

• 3 main types:

• Alpha Radiation

• Beta Radiation

• Gamma Radiation

Alpha Radiation• Occurs when a

helium nuclei is emitted– Called “alpha”

particals

• Product atoms atomic # is lower by 2 & its mass # is lower by 4

• Are stopped by paper!

Beta Radiation• e- released when a

nucleus breaks apart

• Product atom has the same atomic mass, but the atomic # increases by 1

• Less mass than an alpha particle & can penetrate paper, but are stopped by wood or aluminum foil

Gamma Radiation• High energy

photons– Electromagnetic

radiation

• Have no mass or charge, so atomic # is unchanged

• VERY DANGEROUS!– Can penetrate even

wood!

Nuclear Decay• Nuclear force

Attractive force between protons & neutrons that are really close together in the nucleus

• Stronger than the electromagnetic repulsions

• Keeps nucleus together!

Half-Life• Time it takes for

half of the nuclei to decay into its stable daughter