4 forces of nature weak force holds quarks together force of gravity electrostatic force strong...

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4 forces of nature Weak force holds quarks together Force of Gravity Electrostatic force Strong force hold the + charges in the nucleus together

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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

Sources of Radiation

Background

Cosmic radiation

Earth

Food

People

Flying

Medical tests

Cigarettes

Uses in medicine

• TracerI-131

• Irradiation therapyCs-137

Ionizing radiationHow much is safe?

• Biological damage• Radiation effects

Nuclear Reactions

•Radioactive Decay•Nuclear bombardment (Transmutation)•Fission•Fusion

Radioactive Decay

Spontaneous(Natural) emission of• alpha,• beta• gamma• Other radiation

Radioactive decayAlpha emission

Parent alpha + daughter + gamma

Radioactive decayBeta emission

Parent beta + daughter + gamma

Radon

• T ½ = 3 days• Gas• Daughter is a solid

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.

More

Iron-59 has a T ½=45 days. If 2.0 g decay

How many days does it take until .25g remain? W

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

More

What is the half life of I-131 when a 10 g sample decays to .625 g in 80 days?

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 + ?

Particle Accelerators

• Cyclotron• Synchrotron• Linear accelerator• Super conduction supercollider

Transuranium elements

• Elements with atomic number greater than 92

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.

Chain 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

Fusion(joining parts)

See overhead• Naturally in sun• Research in California• Requirements

40,000,000oChigh pressureplasmacontainerelectricity