9/25 Today you will need…  The paper from the side table  We will start nuclear chemistry today by talking about radiation  You will come up with a superhero to save the world from a type of radiation  Answer the following on a clean piece of paper:  1. Draw the nuclear symbol notation for an isotope of silver with a mass number of 109  2. Draw the nuclear symbol notation for an isotope of an element with the atomic number of 11 with 13 neutrons.  3. Draw a Bohr model of Sulfur

CHAPTER 25 Nuclear Chemistry 25.1-Nuclear Radiation 25.2-Radioactive Decay 25.3-Transmutation 25.4-Fission and Fusion of the Atomic Nuclei 25.5-Apllications and Effects of Nuclear Radiation 25.1-Nuclear Radiation 25.2-Radioactive Decay 25.3-Transmutation 25.4-Fission and Fusion of the Atomic Nuclei 25.5-Apllications and Effects of Nuclear Radiation

25.1-Nuclear Radiation Pages

The Nucleus  2 subatomic particles are contained in the nucleus:  Proton  Neutron  Atom referred to in nuclear chemistry as a nuclide.

Nuclear Symbol Notation  Recall the 2 ways to represent an isotope (also called a nuclide):  Hyphen notation Element name-mass number  Nuclear symbol notation-  Atomic number-number of protons  Mass number-number of protons plus neutrons

RadioisotopesRadioisotopes  Isotopes are atoms of the same element that have different numbers of neutrons.  Isotopes of unstable nuclei are called radioisotopes.  These unstable nuclei emit radiation in order to attain more stable atomic configurations in a process called radioactive decay in which atoms lose energy.

Types of Radiation  Alpha particle (  )  helium nucleus paper 2+  Beta particle (  )  electron 1- lead 1+  Gamma (  )  high-energy photon 0 concrete

25.2-Radioactive Decay Pages

Radioactive Decay  Radioactive decay-spontaneous disintegration of a nucleus into a slightly lighter nucleus, accompanied by the emission of particles, radioactive radiation, or both.  Occurs to move an unstable nuclide into the band of stability.  Radioactive nuclide-an unstable nucleus that undergoes radioactive decay.

Nuclear Stability  Nucleus contains most of atoms mass  Protons and Neutrons in nucleus  Held together by strong nuclear forces  Stability of nucleus can be correlated with its neutron/proton ratio  Low atomic numbers have stability of 1:1 ratio. Example: Helium.

Nuclear Stability  When the number of neutrons in a element is plotted as a function of its atomic number, all stable elements fall in a certain range.  Band of stability-stable nuclei cluster over a range of neutron-proton ratios  Elements that fall outside of this band of stability will undergo a nuclear rxn to achieve nuclear stability.

Band of Stability

Nuclear Reactions  Any reaction that affects the nucleus of an atom.  All reactions that we will study later this year involve only the electrons.  In nuclear reaction equations, the total of the mass numbers and the total of the atomic numbers on each side must be equal.

Nuclear Decay  Alpha Emission parent nuclide daughter nuclide alpha particle Numbers must balance!!

Nuclear Decay  Beta Emission electron

Nuclear Decay  Electron Capture electron  Gamma Emission  Usually follows other types of decay.  Transmutation  One element becomes another.

Balancing Nuclear Reactions  When balancing a nuclear reaction,  Decide what mass number and atomic number are needed to balance the eqn.  Determine if what is missing is a nuclide or a radioactive particle.

Balancing Nuclear Reactions  What mass number is needed to balance the equation?  212=4+X, X=208  What atomic number is needed to balance the equation?  84=2+X, X=82  What element or radioactive particle has a mass number of 208 and an atomic number of 82?  Lead-208

Balancing Nuclear Equations

25.3 Transmutation Pages

Half-lifeHalf-life  Half-life (t ½ )  Time required for half the atoms of a radioactive nuclide to decay.  Shorter half-life = less stable.

Calculating Half-life  For each half-life that passes, half of the radioactive nuclide (parent nuclide) decays.  Equations to use for solving ½ life probs:

Half-life Examples  Phophorus-32 has a half-life of 14.3 days. How many milligrams of phosphorus-32 remain after 57.2 days if you start with 4.0 mg of the isotope?  Assuming a half-life of 1599 years, how many years will be needed for the decay of 15/16 of a given amount of radium-226?  The half-life of radon-222 is days. After what time will ¼ of a given amount of radon remain?  A sample contains 4.0 mg of uranium-238. After 4.46X10 9 years, the sample will contain 1.0 mg of uranium-238. What is the half-life of the isotope?

25.4-Fission and Fusion of the Atomic Nuclei Pages

F ission  splitting a nucleus into two or more smaller nuclei  1 g of 235 U = 3 tons of coal

F ission  chain reaction - self-propagating reaction  critical mass - mass required to sustain a chain reaction

Nuclear Power Plants  Use heat from fission reactions to produce electrical energy

FusionFusion  combining of two nuclei to form one nucleus of larger mass  thermonuclear reaction – requires temp of 40,000,000 K to sustain  1 g of fusion fuel = 20 tons of coal  occurs naturally in stars

Fission vs. Fusion  235 U is limited  danger of meltdown  toxic waste  thermal pollution  fuel is abundant  no danger of meltdown  no toxic waste  not yet sustainable FISSIONFISSION FUSIONFUSION

25.5 Applications and Effects of Nuclear Reactions Pages

Nuclear Power  Fission Reactors

Nuclear Power  Fusion Reactors (not yet sustainable) Tokamak Fusion Test Reactor Princeton University National Spherical Torus Experiment

Nuclear Weapons  Atomic Bomb  chemical explosion is used to form a critical mass of 235 U or 239 Pu  fission develops into an uncontrolled chain reaction  Hydrogen Bomb  chemical explosion  fission  fusion  fusion increases the fission rate  more powerful than the atomic bomb