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 (charged particles, uncharged particles, or light) from the nucleus of an atom

The becquerel (symbol: Bq) is the SI derived unit of radioactivity.  1896 Becquerel accidentally develops photo plate with U salts w/o sunlight. Curies conducted experiments and named the “invisible rays” radioactivity. Both won Nobel Prize in Physics, she won for Chem later. Marie Curie died in 1934 of Aplastic anemia.

Source of Nuclear Radiation Strong Nuclear Force binds protons and neutrons together in the nucleus. stronger than electric repulsive force over very short distances. + +

3 Types of Nuclear Radiation Stopped by animation 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

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

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

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. 7

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 8

Quick Quiz. When a radioactive nucleus releases a high-speed electron, the process can be described as oxidation. alpha emission. beta emission. gamma radiation. 9

 Quick Quiz. Which of the following is the symbol of a beta particle? 10