Chemistry Unit 4 Chapter 25 Nuclear Chemistry Mass Defect
Difference between the mass of an atom and the mass of its
individual particles. amu amu Nuclear Binding Energy
Energy released when a nucleus is formed from nucleons. High
binding energy = stable nucleus. E = mc2 E:energy (J) m:mass defect
(kg) c:speed of light (3.00108 m/s) Nuclear Binding Energy
Unstable nuclides are radioactive and undergo radioactive decay.
Types of Radiation 2+ 1- 1+ Alpha particle () Beta particle
(-)
helium nucleus paper 2+ Beta particle (-) electron 1- lead Positron
(+) positron 1+ concrete Gamma () high-energy photon Nuclear Decay
Numbers must balance!! Alpha Emission parent nuclide
daughter nuclide alpha particle Numbers must balance!! Nuclear
Decay Beta Emission electron Positron Emission positron Nuclear
Decay Electron Capture electron Gamma Emission Transmutation
Usually follows other types of decay. Transmutation One element
becomes another. IQ# 1 Balance the following equations: Nuclear
Decay Why nuclides decay
need stable ratio of neutrons to protons Band of Stability and
Radioactive Decay Half-life Half-life (t)
Time required for half the atoms of a radioactive nuclide to decay.
Shorter half-life = less stable. Half-life mf:final mass mi:initial
mass n:# of half-lives Half-life t = 5.0 s mi = 25 g mf = ? total
time = 60.0 s
Fluorine-21 has a half-life of 5.0 seconds.If you start with 25 g
of fluorine-21, how many grams would remain after 60.0 s? GIVEN: t
= 5.0 s mi = 25 g mf = ? total time = 60.0 s n = 60.0s 5.0s =12
WORK: mf = mi ()n mf = (25 g)(0.5)12 mf = g Fraction left after 5
half-lives = 500g (0.5)5 Mi = 500 g n = 5 Mf = ?
Example: How much of a 500. g sample of Uranium-235 would be left
after five half-lives? Example:A mg sample of Radon-222 decays to
mg after 24 hours.Determine the half-life. Fraction left after 5
half-lives = 500g (0.5)5 Mi = 500 g n = 5 (n = # of half-lives) Mf
= ? Mf = g 16 8 42 1 0.5 0.25 = 6 half lives Example: The half-life
of molybdenum-99 is 67 hours. How much of a 1
Example: The half-life of molybdenum-99 is 67 hours.How much of a
mg sample is left after 335 hours? Mi = mg Half-life = 67 h Rxn
time = 335 h Mf = ? n = 335 / 67 = 5 Mf = mg Learning Check! The
half life of I-123 is 13 hr.How much of a 64 mg sample of I-123 is
left after 39 hours? Half Life and Radioactivity Lab
Work in groups of 2 at your table. Each cup has 1 penny in it which
will be shaken and then GENTLY emptied on the table. For the first
trial, shake the penny out 100 times on the table. Record the
number of times that it came up heads. For the next trail, you will
shake out the penny the number of times that it landed on heads in
the last round. The same procedure will follow until no more of the
pennies have landed on heads (tails = decayed). Record all data in
the lab book following the example on page 809. Answer questions
1-4 and be sure to follow the graphing rules (R74 and in the Math
Review handout from the beginning of the year). Graphing the
Results Important !! Graph directly on lab book
Title every graph and label each axis Graph at least 2/3 page Use a
ruler Circle all data points Use a best-fit line (no connect the
dots!) 5) Find the average half-life (in # of trials) of your
sample by interpolating your curve at exactly 50, 25, and 12.5
flips) F ission splitting a nucleus into two or more smaller
nuclei
1 g of 235U =3 tons ofcoal F ission chain reaction -
self-propagating reaction
critical mass -mass requiredto sustain achain reaction Fusion
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 instars Fission
vs. Fusion 235U is limited danger of meltdown toxic waste
thermal pollution fuel is abundant no danger of meltdown no toxic
waste not yet sustainable Nuclear Power Cooling Tower Fission
Reactors Nuclear Power Fission Reactors Nuclear Power Fusion
Reactors (not yet sustainable) Nuclear Power Fusion Reactors (not
yet sustainable)
National Spherical Torus Experiment Tokamak Fusion Test Reactor
Princeton University Synthetic Elements Transuranium Elements
elements with atomic #s above 92 synthetically produced in nuclear
reactors and accelerators most decay very rapidly Radioactive
Dating half-life measurements of radioactive elements are used to
determine the age of an object decay rate indicates amount of
radioactive material EX: 14C - up to 40,000 years 238U and 40K -
over 300,000 years Radiation treatment using
Nuclear Medicine Radioisotope Tracers absorbed by specific organs
and used to diagnose diseases Radiation Treatment larger doses are
usedto kill cancerous cellsin targeted organs internal or
externalradiation source Radiation treatment using -rays from
cobalt-60. Nuclear Weapons Atomic Bomb Hydrogen Bomb
chemical explosion is used to form a critical mass of 235U or 239Pu
fission develops into an uncontrolled chain reaction Hydrogen Bomb
chemical explosion fission fusion fusion increases the fission rate
more powerful than the atomic bomb Others Food Irradiation
Radioactive Tracers Consumer Products
radiation is used to kill bacteria Radioactive Tracers explore
chemical pathways trace water flow study plant growth,
photosynthesis Consumer Products ionizing smoke detectors -
241Am
Top Related