Chapter 19Chapter 19

Nuclear ChemistryNuclear Chemistry

Marie Sklodowska Curie

Types of Nuclear Types of Nuclear ReactionsReactions

1. Radioactive Decay1. Radioactive Decay

Emission of an alpha (Emission of an alpha () particle, ) particle, beta (beta () particle, or gamma () particle, or gamma () ) radiation radiation results in slightly results in slightly lighter and more stable nucleilighter and more stable nuclei

2. Nuclear disintegration2. Nuclear disintegration

Nucleus bombarded with particles Nucleus bombarded with particles (e.g. (e.g. ,p+, n,p+, n00) ) nucleus emits p nucleus emits p++ or or nn00 and becomes more stable and becomes more stable

3. Fission3. Fission

Very heavy nucleus splits to form Very heavy nucleus splits to form medium mass nucleimedium mass nuclei

4. Nuclear Fusion4. Nuclear Fusion

Light mass nuclei combine Light mass nuclei combine form form heavier, more stable nucleiheavier, more stable nuclei

RadioactivityRadioactivity

Spontaneous disintegration of Spontaneous disintegration of unstable nuclei unstable nuclei emitted emitted

e.g. U-238, radium (Ra-226)e.g. U-238, radium (Ra-226)

Types of radiation Types of radiation

Alpha (Alpha ())

Helium nucleusHelium nucleus 22++ chg. chg. Moves at 1/10 cMoves at 1/10 c Low penetrating powerLow penetrating power

Beta (Beta ())

ElectronsElectrons 1- chg1- chg Moves at close to cMoves at close to c 100x penetrating ability of 100x penetrating ability of

Gamma (Gamma ())

Electromagnetic wavesElectromagnetic waves 0 chg0 chg Highest penetrating powerHighest penetrating power

Half LifeHalf Life

Time during which half of a given # Time during which half of a given # of atoms of a radioactive isotope of atoms of a radioactive isotope decaysdecays

Half Life exampleHalf Life example

If you start with 7.0g of radioactive If you start with 7.0g of radioactive Radon-222 (half life = 3.823 days) how Radon-222 (half life = 3.823 days) how many g remain after 11.47 days?many g remain after 11.47 days?

# half lives = time elapsed x 1 half life/ # half lives = time elapsed x 1 half life/ 3.823 days3.823 days

Original amt. of Radon-222 remaining Original amt. of Radon-222 remaining x ½ for each half life = amt. of radon-x ½ for each half life = amt. of radon-222 remain.222 remain.

(cont.)(cont.)

3 half lives = 11.47 days x 1 half life/ 3 half lives = 11.47 days x 1 half life/ 3.823 days3.823 days

7.0g x ½ x ½ x ½ = 0.88 g Radon-7.0g x ½ x ½ x ½ = 0.88 g Radon-222222

Properties of naturally Properties of naturally occuring radioactive occuring radioactive

isotopesisotopes Expose filmExpose film Produce electric chg. in surrounding Produce electric chg. in surrounding

air (Geiger counter)air (Geiger counter)

properties (cont.)properties (cont.)

Cause fluorescence when mixed with Cause fluorescence when mixed with certain cmpdscertain cmpds

Properties (cont.)Properties (cont.)

Physiological effects Physiological effects e.g. medical treatments, killing e.g. medical treatments, killing

bacteriabacteria

Properties (cont.)Properties (cont.)

DecayDecay Radioactive isotopes decay into simpler Radioactive isotopes decay into simpler

atomsatoms

Nuclear equationsNuclear equations

Transuranium elementsTransuranium elements

Elements with more than 92 protons Elements with more than 92 protons First two produced were neptunium First two produced were neptunium

and plutoniumand plutonium

ApplicationsApplications

1. Radioactive dating1. Radioactive dating

radioactive substances decay at known radioactive substances decay at known ratesrates

Rates are constantRates are constant % parent v. daughter isotopes % parent v. daughter isotopes age of age of

materialmaterial e.g. C-14 dating of ancient Egyptian e.g. C-14 dating of ancient Egyptian

lumber lumber ½ radiation of carbon in living ½ radiation of carbon in living trees, half life of carbon-14 is 5730 yrs., trees, half life of carbon-14 is 5730 yrs., therefore lumber is 5700 yrs. oldtherefore lumber is 5700 yrs. old

2. Radioisotopes in 2. Radioisotopes in medicinemedicine

3. Nuclear Power Plants3. Nuclear Power Plants

Nuclear chain reaction Nuclear chain reaction

4. Nuclear Fusion4. Nuclear Fusion

‘‘ultimate’ energy sourceultimate’ energy source Occurs in stars, e.g. the sunOccurs in stars, e.g. the sun 100,000,000 K temp 100,000,000 K temp