Download - NUCLEAR CHEMISTRY
NUCLEAR CHEMISTRYAn Energetic Concept
WHO DID WHAT
Wilhelm RoentgenLaboratory generated
phosphorescenceX-rays
WHO DID WHAT
Henri BecquerelInherited U salts (pitchblende)Natural phosphorescenceDiscovered spontaneous
phosphorescence
WHO DID WHAT
Marie & Pierre CurieStudied Becquerel
phosphorescence and named itDiscovered Po, Ra
ISOTOPE REVIEW
XA
Z
A—mass number
Z—atomic number
A – Z = number of neutrons
SO, WHAT IS RADIATION?
Instability due to n:p+
RadioisotopesGoal is stability
SO, WHAT IS RADIATION?
TYPES OF RADIATION
RutherfordElectric field effect on
radioactivityAlphaBetaGamma
TYPES OF RADIATION
TYPES OF RADIATION
Alpha ()Same as a He-4 nucleusA decreases by 4Z decreases by 2
TYPES OF RADIATION
AlphaNot very penetrating
Stopped by a sheet of paperVery ionizing
TYPES OF RADIATION
Beta ()Same as an electronA remains the sameZ increases by 1
e
TYPES OF RADIATION
BetaMore penetrating than
Stopped by a thin sheet of metal
Less ionizing than
TYPES OF RADIATION
Gamma ()Pure energyUsually accompanies and More penetrating than and
Somewhat blocked by several inches of Pb or several feet of concrete
Less ionizing than and
TYPES OF RADIATION
Positron (+)Same mass as Opposite charge of
F O + e18
9
18
8
0
+1
TYPES OF RADIATION
Electron captureThe opposite of emissionA remains the sameZ decreases by 1
DECAY SERIES
Continued radiation until stableFr-221 undergoes the following
decay series: ,,,,,
Fr At + He221 87
217 85
4 2
At Bi + He217 85
213 83
4 2
Bi Tl + He213 83
209 81
4 2
Tl Pb + e209 81
209 82
0 -1
Pb Bi + e209 82
209 83
0 -1
Bi Tl + He209 83
205 81
4 2
RATE OF RADIOACTIVE DECAY
Half-Lifet½ = 0.693/k
k = rate law constantFirst-order Kinetics
lnN = –kt + lnNo
N…amount after elapsed timet = elapsed timeNo = amount originally
UNITS OF RADIOACTIVE DECAY
curie (Ci)1 Ci = 3.7 x 1010 disintegrations per second
~activity of 1 g of Ra-226becquerel (Bq)
SI unit1 Bq = 1 dis/s…37 GBq = 1 Ci
UNITS OF RADIATION EXPOSURE
sievert (Sv)Dose absorbed by specific
tissueReplaced röntgen equivalent to
man (rem)1 Sv…nausea2-5 Sv…hair loss, hemorrhage3 Sv…death in 50% of people in
30 days>6 Sv…unlikely survivalTypical background exposure is
2.4 mSv/year
RATE OF RADIOACTIVE DECAY
The half-life of F-18 is 2 hours. If you receive a dose of 200 mCi at 8:00 AM, how long will it take for 10 mCi to remain in your body? At what time will you have 10 mCi in you?Solve for the value of kPlug into the linear equation
and solve for t
RATE OF RADIOACTIVE DECAY
2 h = 0.693/k…
k = 0.3465 h-1
ln(10 mCi) = –(0.3465 h-1)(t) + ln(200 mCi)
ln(10 mCi) – ln(200 mCi) = –(0.3465 h-1)(t)
– 2.996= –(0.3465 h-1)(t)
8.65 h = t
at 4:39 PM, you will have 10 mCi in you
RADIOACTIVE DATING
C-14 is a beta emitter with a half-life of 5730 years
Used to determine the age of carbon-based substances