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4 forces of nature
• Weak forceholds quarks together
• Force of Gravity
• Electrostatic force
• Strong force
hold the + charges in the nucleus together
alpha beta gamma
Symbol 4He , α2
0 e , β-1
0 γ0
Size Large Small No size
Charge +2 -1 O charge
Speed Slow Fast Speed of light
Shielding Paper/skin
Metal foil
Inches lead
Identity Helium nucleus
electron
Wave of energy
Lab: Half-life
Purpose: To simulate radioactive decayReaction: Parent Daughter +
radioactivityM no M
Data table:# half-lives # decayed# undecayedO (no M) 0 (M)40Each shake will simulate 1 half life.
Half-life
•The time for ½ the amount of a parent to decay to a daughter
• Set up a chart# half lives Time Amount
0 0
Try this!
N-13 emits beta . If 2.0g decay and the half life is T1/2 = 10 min
a. How long is 4 half lives?b. How many grams remain?c. Write the decay reaction.
Try another
• Manganese-56 is a beta emitter with T1/2=2.6 hr.
• What is the mass of a 10 g
sample after 10.4 hrs? • How many half lives is this?• Write the radioactive decay
reaction.
Try another
• Manganese-56 is a beta emitter with T1/2=2.6 hr.
• What is the mass of a 10 g
sample after 10.4 hrs? • How many half lives is this?• Write the radioactive decay
reaction
Nuclear bombardmenttransmutation
• Emission of radiation after a nucleus is hit by a particle causing it to change to another element
Nuclear bombardment
•1919 RutherfordN-14 + alpha proton + ?
•1932 ChadwickBe-9 + alpha carbon-12 + ?
•1934 CurieAl–27 + alpha P-30 + ?P-30 Si-30 + ?
C-14 dating
• N-14 + n C-14 + Proton in air
• C-14 + O2 CO2-14 we breathe it in
• C-14 N-14 + beta• Know what is in living• Measure what is in dead
• Know the T ½
• Do half life problem to calculate time
Problem
• The living organism has 15g C-14• The half life is 5,730 year• If the dead organism has .95g of C-
14, how long has it been dead?
Nuclear Fission splitting the atom
• WWII Hahn, Strassman, Meitner• Manhattan Project
Los Alomos New MexicoFat Man, Little Boy
U-235 + 1 N Ba-141 + Kr-92 + 3 N + Energy
E=mc2
E=m(3.00x108m/sec)2
Law of Conservation of Matter is only valid for chemical reaction. In nuclear reactions the mass is changed into lots of energy
Nuclear Binding Energy
He nucleus 4.0026 amu, what is binding energy?
1 proton = 1.0078 amu
1 neutron = 1.0087 amu
E= J= 1
1 amu = 1.66 x 10-27 g
Nuclear Reactorssteam is made to generate electricity
• Fuel U-235• Moderator slows down neutrons• Control rods absorb neutrons• Shielding concrete• Coolant water
Critical mass – mass needed to keep a nuclear reaction going
Chain reaction – reaction where a neutron starts the reaction and is produced in the reaction.
Nuclear waste
• High levelspent fueldefense waste
• Low levelProtective clothingMedical radioisotopesAir filters
Nuclear Fission splitting the atom
• WWII Hahn, Strassman, Meitner
• U-235 + 1 Neutron 2 medium + 3 neutrons + Energy
See overhead
Fusion(joining parts)
See overhead• Naturally in sun• Research in California• Requirements
40,000,000oChigh pressureplasmacontainerelectricity