Radioactivity

Do Now (5/2/12):What is an istope?What makes an isotope different than its element?Nuclear Reactions 5/2/12 Lesson Objectives Describe nuclear reactions and perform balancing of nuclear reactions by solving problems.Apply radioactivity equations by solving problems. Isotope Atomic nuclei having the same number of protons but different number of neutrons Vocab Review:Nuclear reaction: A reaction in which the number of protons or neutrons in the nucleus of an atom changes.Atomic number: Number of protons in the nucleus of the atomMass number: Sum of protons and neutrons in the nucleus of the atom

Format Alpha decay Radioactive decay process in which the nucleus of an atom emits an alpha particle

Alpha ParticleNucleus of a helium atom

Beta decay Radioactive decay that occurs when a neutron is changed to a proton within the nucleus of an atom, and a beta particle and an antineutrino are emitted Gamma decay Radioactive process of decay that takes place when the nucleus of an atom emits a gamma ray.http://library.thinkquest.org/17940/texts/radioactivity/radioactivity.html

Mass Defect: The difference between the sum of the mass of the individual nucleon (proton or neutron) and the actual mass.

Example #1:Fermium-253 has a half-life of 0.334 seconds. A radioactive sample is considered to be completely decayed after 10 half-lives. How much time will elapse for this sample to be considered gone?Binding EnergyThe energy equivalent of the mass defect; it is always negative It is the minimum amount of energy needed to break the nucleus into its component nucleons.

Example #2:The half life of Zn-71 is 2.4 minute. If one had 100 g at the beginning, what is the decay rate of Zn-71?Mass remainingm=mass remainingOriginal mass

Example #3:The half life of Zn-71 is 2.4 minute. If one had 100 g at the beginning, how many grams would be left after 7.2 minutes elapsed?Practice:Use the rest of class to work on the paper: Radioactivity; problems: #2,5,6, and 7Do Now (4/24/12):Pd-100 has a half-life of 3.6 days. If one had 6.02x1023 atoms at the start, how many atoms would be present Anti-MatterPair ProductionWhen an electron and a positron collide, the two can annihilate each other, resulting in energy in the form of gamma rays. In this process, called annihilation, matter is converted directly into energy. The inverse of annihilation can also occur where energy is converted directly into matter. The inverse of annihilation is called pair production.

Pair Production

The Standard Modelexplains what the world is and what holds it together. explains all the hundreds of particles and complex interactions. made up ofQuarksLeptonsForce carriers

Quarks Six flavors (three pairs): up/down, charm/strange, and top/bottom.for each of these quarks, there is a corresponding antiquark.fractional electric charge, unlike the proton and electron, which have integer charges of +1 and -1 respectively. Quarks also carry another type of charge called color charge.

Hadrons Composite particles made of quarksindividual quarks have fractional electrical charges, so hadrons have a net integer electric charge. no net color charge even though the quarks themselves carry color chargeTwo classesBaryons...are any hadron which is made of three quarks (qqq).

Because they are made of two up quarks and one down quark (uud), protons are baryons. So are neutrons (udd).

Mesons...contain one quark (q) and one antiquark.

Ex: pion (+), which is made of an up quark and a down anitiquark. an antipion (-) is made up a down quark and an up antiquark. a meson consists of a particle and an antiparticle, so it is very unstable.

Leptons six leptons; three have electrical charge and three do not.The three charged leptons are the electron (e-), muon() and the tau(), Three types of neutrinos (). They have no electrical charge, very little mass, and are hard to find. For each lepton there is a corresponding antimatter antilepton. anti-electron = the "positron. LeptonsQuarks are sociable; only exist in composite particles with other quarksleptons are solitary particles.charged leptons as independent cats with associated neutrino fleas, which are hard to see.

Do Now (4/24/12):U-238 has a half-life of 4.46x109 years. How much U-238 should be present in a sample 2.5 x10 10 years old, if 2 grams were present initially?