Radioactivity

• Some substances spontaneously emit radiation – radioactivity

• The rays and particles emitted are called “radiation”.

• Radioactive elements change their identity – they can change into another element– They do this because the nuclei are unstable

– Changes to atom’s nucleus is called a nuclear reaction Something else Dalton got wrong.

Radioactive Decay

• Radioactive elements emit energy as radiation

• This is called ‘radioactive decay’

• Unstable atoms undergo radioactive decay until they form stable atoms

Types of Radiation

• Alpha Radiation – emitting a positively charged particle - α

• Beta Radiation – emitting a negatively charged particle - β

• Gamma Radiation – High energy radiation with no mass - γ

Alpha Radiation

• Alpha radiation– Made up of

Alpha particles– Alpha particles

have 2 protons, 2 neutrons

– Alpha particles have a 2+ charge

α

Nuclear EquationsNuclear Equations transmutation - an element is transformed into a new element. This can occur by natural or artificial means.

loss of an particle radium is emitting an particle                                                     

+

Beta Radiation

• Beta Radiation is fast moving electrons– Attracted to positive charged items– Charge is 1-

Gamma Radiation

• High Energy radiation with no mass– No charge– Usually accompany alpha and beta radiation– Account for most of the energy lost during

radioactive decay

Review

• Classify each as a chemical reaction, nuclear reaction, or neither

• Thorium emits a beta particle:– Nuclear

• Two atoms share electrons to form a bond:– Chemical

• A sample of pure sulfur emits heat as it slowly cools:– Neither

• A piece of iron rusts:– chemical