Introduction to Radioactivity
Radioactivity is the spontaneous emission of radiation from unstable atomic nuclei. Understanding radioactivity is important in medicine, energy production, and understanding the age of the Earth and universe.
What You Need to Know
Key Concept Diagram
Radioactive decay occurs when unstable nuclei lose energy by emitting particles or radiation
Alpha particles (alpha): relatively large, positively charged; stopped by paper or a few cm of air
Beta particles (beta): fast-moving electrons; stopped by thin aluminium
Gamma rays (gamma): high-energy electromagnetic radiation; reduced by thick lead or concrete
Half-life: the time for half of a radioactive sample to decay; used in carbon dating and nuclear medicine
Key Vocabulary
Radioactivity
The spontaneous emission of radiation (alpha, beta, or gamma) from unstable atomic nuclei
Alpha Particle
A positively charged particle (2 protons + 2 neutrons) emitted during radioactive decay; low penetrating power
Half-life
The time taken for half the radioactive atoms in a sample to decay into a different element
Ionising Radiation
Radiation with enough energy to remove electrons from atoms, potentially damaging living cells
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
Which type of radiation has the LEAST penetrating power?
Question 2
A radioactive sample has a half-life of 10 years and initially contains 800 g. How much remains after 30 years?
Question 3
Which medical application uses radioactivity?
Key Concepts Summary
- ●Radioactive decay occurs when unstable nuclei lose energy by emitting particles or radiation
- ●Alpha particles (alpha): relatively large, positively charged; stopped by paper or a few cm of air
- ●Beta particles (beta): fast-moving electrons; stopped by thin aluminium
- ●Gamma rays (gamma): high-energy electromagnetic radiation; reduced by thick lead or concrete
- ●Half-life: the time for half of a radioactive sample to decay; used in carbon dating and nuclear medicine