Nuclear Chemistry

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Objectives: Explain how unstable nuclei release energy Describe the three main types of nuclear radiation Solve problems that involve half-life Identify the two ways transmutation can occur Describe what happens in a nuclear chain reaction Explain the role of water in the storage os spent fuel rods Distinguish fission from fusion reactions Identify three devices used to detect radiation Describe how radioisotopes are used in medicine Created by C. Ippolito May 2007

Radioactivity



Antoine Becquerel, Marie and Pierre Curie

 studied rays from uranium “exposed” film 

Radioactivity

 the process of “releasing” rays 

Radiation

 penetrating rays and particles released 

Radioisotopes



unstable nuclei

release energy during

radioactive decay

Created by C. Ippolito May 2007

Types of Radiation



Alpha Radiation

( α )  4 two protons and two neutrons ( )  226

Ra

88  222

Rn

86  2 4

He

Beta Radiation

( β ) 0 1

n

   electron ( ) or positron ( ) 1 1 1

H

 0  1

e

14

C

6  14

N

7  0  1

e

Gamma Radiation

1 1 ( γ )

H

 0 1

n

 0  1

e

19 10

Ne

  high energy photon 60

Co

27  56

Mn

25  2 4

He



gamma ray

Created by C. Ippolito May 2007  0

e

 19 9

F

Shielding

paper or cloth

Composition

alpha particle He nucleus

Symbol

α, 2 4

He

Alpha Radiation

Penetrance

low 0.05 mm

Charge

2+

Source

Radium-226 Created by C. Ippolito May 2007

Mass

4 amu

Shielding

metal foil

Composition

beta particle, electron

Symbol

β, 0  1

e

Beta Radiation

Penetrance

moderate 4 mm

Charge

1-

Source

Carbon-14

Mass

1/1837 amu Created by C. Ippolito May 2007

Shielding

lead, concrete

Composition

electromagnetic radiation

Symbol

γ

Penetrance

very high

Gamma Radiation

Charge

0

Source

Cobalt 60 Created by C. Ippolito May 2007

Mass

0

Nuclear Stability and Decay



Nuclear Force

 holds all nuclear particles together  stronger than electromagnetic forces 

Band of Stability

 neutron to proton ratio for stable nuclei Created by C. Ippolito May 2007

Half-Life

 

Half-life

 (t ½ ) time required for one-half of the nuclei of a radioisotope to decay to products  after each half-life, half of the existing radioactive atoms have decayed into atoms of a new element Table N – Radioisotopes  half-life  decay type Created by C. Ippolito May 2007

Half-life Calculations

Created by C. Ippolito May 2007

Transmutation

 an atom of one element turns into an atom of another element  TWO WAYS:  radioactive decay  particle bombardment 

transuranium elements

 all elements above 92  synthesized by bombardment in reactors and particle accelerators Created by C. Ippolito May 2007

Nuclear Fission

   

Fission

  neutron bombardment of isotopes splits nuclei into fragments energy released used to produce steam in power plants to run dynamos

Chain Reaction

 neutron produced react with other atoms producing more neutrons

Neutron Moderation

 slow down neutrons so reactor fuels can capture them to maintain chain reaction

Neutron Absorption

  decreases number of slow neutrons to slow down or stop reaction “control rods” usually made of cadmium Created by C. Ippolito May 2007

Nuclear Fusion

 Fusion  nuclei combine to produce a nucleus of greater mass  occurs in the sun Created by C. Ippolito May 2007

Detecting Radiation



Geiger Counter

 gas filled tube detects radiation ( α,β, γ) 

Scintillation Counter

 phosphor coated surface detects radiation ( α,β, γ) 

Film Badge

 several layers of photographic film  used to determine exposure of workers Created by C. Ippolito May 2007

Radiation Usage



Medical Diagnosis

 radioisotope tracers follow metabolic paths 

Medical Treatment

 destroy cancerous cells 

Radioactive Dating

 determine age of fossils Created by C. Ippolito May 2007