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Three types of radioactivity observed for radium
1)α (alpha)
particles
2)β (beta)
particles
3)γ(gamma)
rays
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Number of disintegrations is______ to
number of atoms
proportional
-
Decay equations
A=A0e(-.693/T1/2)t
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Radioactivity was discovered by ____in ____.
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Activity is defined as:
material A
the rate of decay of a radioactive
-
ΔN/Δt=
-λN
(the change in the number of atoms divided by the change in time =the negative decay constant times the number of atoms)
-
Specific
activity ≡
activity per unit mass
-
-
One Curie = _______dps
3.7 × 10 10 dps
- –approx.
- activity of 1 g Radium, now 3.61x1010 dps)
-
Becquerel
(Bq) =__disintegration/second
1
-
-
-
-
1MBq =__Bq = __dps
1 MBq =106 =106 dps
1GBq = 109Bq =109dps
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Mean life or average life (Tave)
is ____________.
time it would take source decaying with constant (initial) activity to decay completely
-
The mean life equation:
1.44*T1/2
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Cumulative activity =
A0*mean life(1.44*T1/2)
-
Total # of disintegrations =
Activity*1.44*T1/2
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Total dose=
mean life * initial dose
(1.44 * T1/2 * initial dose)
like for LDR implants
-
Applications that use mean life:
- total dose (mean life * initial dose)
- total disintegrations (mean life * activity)
- cumulative activity (mean life * original activity)
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Radioactive isotopes of lighter elements
achieve stability by keeping ____constant through ____or______.
- mass number
- beta decay
- K capture (K-shell electron which is captured)
-
how does magnetic field affect gamma rays?
it doesn't, because it has no charge
-
Are alpha particles or beta particles bent more by a magnetic field?
beta
-
which unit is smaller, a Bq or a Ci?
Bq is much smaller than a Ci
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All nuclei with Z>___ are unstable and lose mass by ___ decay. Naturally occurring isotopes occur in the (name 3) series.
- 82 (heavy nuclei)
- alpha
- (they also emit gamma and beta)
- Uranium, Thorium, Actinium
-
Radioactive equilibrium occurs when the half life of the“daughter” product is:
- occurs when the half life of the
- “daughter” product is less than the half life of the parent
-
There are two types of radioactive equilibrium-
what are they and which involves a generator("cow")?
- Transient("cow") -used in nuke med
- Secular
-
In _____equilibrium, the daughter's half life is much less than the 1/2 life of the parent
secular
an example would be 226Ra (T1/2=1622 y) and daughter 222Ra (T1/2=3.8 d)
-
This is an example of "milking the cow" or transient equilibrium
-
-
All matter is composed of ____,
distinguished by physical and chemical properties of its _____.
-
Radius of atom:
radius of nuclues
-
Primary Beam:
Particles which have not experienced collision
-
-
Particles which have experienced collisions
-
The secondary beam is also known as the:
scattered beam
-
The nucleus is composed of:
- protons(+)
- and
- neutrons(no charge)
-
A=
mass number (number of protons +neutrons)
-
Isotopes:
same # protons
different # neutrons
-
Isotones: =
- same # neutrons
- different # protons
-
Isobars:
same # nucleons
different# protons
-
Isomers:
- same # protons
- same #neutrons
- nucleus different energy state
-
Nuclei gain stability when:
neutrons and protons are evenly paired
But as the Z increases, more neutrons are needed (n/p greater than 1)
-
Nuclei gain stability for
Z< 20 when the n/p is:
~ 1.0
-
Nuclei gain stability for
Z> 20 when the n/p is:
>1.0
(Z GREATER than 20
n/p GREATER than 1)
-
-
-
Unit charge =
- 1.6 x 10-19 C
- any single electron or proton carries this charge
-
Atomic weight (AW)= mass of atom in amu
mass of atom in amu
-
Gram atomic mass =
the mass, in grams, of one mole of atoms in a monatomic chemical element
Mass in grams = atomic weight = 1 mole
-
define mole
The mole is a unit of measurement for amount of substance. It is defined as the amount of any chemical substance that contains as many elementary entities, e.g., atoms, molecules, ions, or electrons, as there are atoms in 12 grams of pure carbon-12 (12C),
-
Avogadro’s number =
6.022 x 1023 atoms
-
# atoms/g =
- NA/AWAvogadro's Number/Atomic weight
-
# electrons/g =
(NA x Z)/AW
-
What is the mass defect?
Total Mass of the atom < sum of its constituent parts
The mass defect (difference) is the binding energy of the nucleus(nuclear force)
-
Mass and energy equivalence:
E = mc2
-
-
1 MeV=____eV
1 MeV = 1 x 106 eV
-
The number of electrons which can occupy a shell = 2n2
2n 2
*Remember n= the shell # K=1 - L=2 etc.
-
Binding energy (increases/decreases) as distance to nucleus decreases .
- Binding energy (increases/decreases) as distance to nucleus decreases
- (potential energy decreases)
-
Characteristic radiation – energy=
difference in electron orbital energy
-
If sufficient energy is transferred to an orbital electron, it is:
ejected from the atom
-
What are the four forces in nature?
- 1)Gravitational
- 2)Electromagnetic
- 3)Weak nuclear
- 4)Strong nuclear
-
Which force is responsible for decay?
weak nuclear
-
Strong nuclear force - creates:
- “potential well” for particles within
- also keeps particles in nucleus
-
Which force creates “potential barrier” for approaching charged particles?
Electrostatic (Coulomb) force
-
Protons, neutrons, electrons, and other subatomic particles can travel at high speeds (approaching speed of light) and:
transfer energy.
-
EM radiation is produced by oscillating:
EM fields
-
EM radiation is energy propagated at the speed of:
light (c)
-
Electromagnetic Radiation Wave Model
c=?
- c=vλ
- v-frequency in cycles per second
- λ=wave length(distance between two peaks)
-
Photon E=
E=hv= hc/λ
- h=plank's constant (6.62 * 10 -34 )
- E is in eV
- λ is in m
-
Energy of photons equation(shortcut)
-
Ionization takes place beyond a specified _______.
energy
-
-
Types of radioactive decay:
)α – particle decay
2)β particle decay
a)β+ positron emission
b)β- negatron emission
3)Electron capture–alternative to positron emission
4)Internal conversion–isomeric transitionα –
-
alternative to positron emission?
Electron capture
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