3 The Four Universal Forces Gravitational forceElectromagnetismWeakStrong
4 Who Discovered Radioactivity? In 1896, Henri Becquerel, along with Pierre and Marie Curie discovered radioactive waves by placing a rock containing Uranium on a photographic plate. They shared the Nobel Prize in 1903.
5 What is Radioactive Decay? Radioactive decay is the set of various processes by which unstable atomic nuclei emit subatomic particles (radiation).Decay is said to occur in the parent nucleus and produces a daughter nucleus.
6 Types of Particles Identity Symbol Charge Mass (amu) Helium (Alpha) 4 α2+2Electron(Beta)0 β-1Photon (gamma)0 γN/ANeutron1 nProton1 p1+1Positron
7 What are their properties? Alpha: largest particle, can be stopped by paperBeta: can be stopped by a few layers of clothingGamma: most penetrating, stopped by lead
10 Half-life: The time it takes for half the element to decay
11 Half Life Calculations To calculate the ½ lifet1/2 = log 0.5___log(No/N)N = amount remainingNo = amount you started witht = time elapsedt1/2 = half lifex t
12 Half - LifeThe half life of I-123 is 13 hours. How much of a 64 mg sample is left after 26 hours?No = 64 mgt = 26 hourst1/2 = 13 hoursHow many half lives have passed?N = 64 x (0.5)2N = 16 mg remaining
13 Half - Life Isotope Half - Life Carbon-15 2.4 seconds Radium-224 3.6 daysRadium-22312 daysIodine-12560 daysCarbon-145700 yearsUranium-235710,000,000 years
14 What is the difference between Fission and Fusion? Fission: Splitting of atomic nucleus (nuclear power plant)Fusion: Fusing of atomic nuclei (sun)Both release large amounts of energy
15 What Are The Uses of Radioactivity? There are many practical applications to the use of radioactivity/radiation.Radioactive sources are used to study living organismsTo diagnose and treat diseasesTo sterilize medical instruments and foodTo produce energy for heat and electric powerTo monitor various steps in all types of industrial processes.To determine age of fossils