Nuclear Radiation ??? Radioactivity (Nuclear Decay) Henri′ Becquerel Marie Curie ??? 1896 Becquerel accidentally develops photo plate with U salts w/o sunlight Curies exp. and named it radioactivity. Both won Nobel Prize in Physics, she won for Chem later. Died 1934 leukemia. Radioactivity (Nuclear Decay) spontaneous emission of high-energy radiation or charged particles from the nucleus of an atom

3 Types of Nuclear Radiation 2 p + 2 n Alpha (a) + Beta (b–) e– Gamma (g)

3 Types of Nuclear Radiation Penetrating: Least to Most (damaging)  –  Video clip is “Radioactivity” from Safari playlist (4 min) or Concrete

3 Types of Nuclear Radiation Stopped by Symbol Charge Mass Alpha Particle () helium nucleus +2 4 paper Beta Particle (–) electron (smaller, faster) aluminum –1 Gamma Ray () high-energy light (fastest) 3 feet of Concrete or Lead

Nuclear Decay Rates Half-Life

Certain elements are radioactive because their atoms have Quick Quiz! Certain elements are radioactive because their atoms have more neutrons than electrons. an unstable nucleus. a small nucleus. more neutrons than protons. 8

Which property does NOT describe an alpha particle? Quick Quiz. Which property does NOT describe an alpha particle? +2 charge a relatively large mass a negative charge low penetrating power 9

Quick Quiz. When a radioactive nucleus releases a high-speed electron, the process can be described as oxidation. alpha emission. beta emission. gamma radiation. 10

 Quick Quiz. Which of the following is the symbol of a beta particle? 11