Natural Radioactivity: the spontaneous breakdown of atomic nuclei, accompanied by the release of some form of radiation
A) Transmutation: the conversion of one element to another by means of a nuclear change
B) To detect Radioactivity one could use Geiger Counter
C) Types of Radioactive emissions (emanation)
All differ in mass, size and charge
1) Alpha Particle: ^{4}_{2}a
v ___positive 2 charge_________
v ___helium nucleus____________
v ____mass of 4amu
Example: ^{226}_{88}Ra ® ^{222}_{86}Rn + ^{4}_{2}He
2) Beta Particle: ^{0}_{1}b
v __negative charge____________
v __acts like a high speed electron
v __no mass______________________
Example: ^{235}_{92}U ® ^{235}_{93}Np + ^{0}_{1}b
3) Gamma Radiation (NOT a Particle) g
v __no charge____________________
v __acts like a high speed xray but with a lot more energy
v __no mass______________________
4) Positron Particle: ^{0}_{+1}b
v __positive 1 charge_________
v __acts like positive electrons
v __no mass_____
Summary of Radioactive emanations:
Particle

Symbol

Mass

Charge

Relative Penetrating Power

alpha

^{4}_{2}a

4amu

+2

low

beta

^{0}_{1}b

0

1

moderate

gamma

g

0

0

high

positron

^{0}_{+1}b

0

+1

moderate

***opposites attract, like charges repel
D) Halflife: the time it takes for half of the atoms in a given sample of an element to decay
*Some selected halflives are found on Table N
*All reactions on Table N are Natural Transmutation
*Formulas for halflife reactions are found on Table T
1) Fraction Remaining = (1/2)^{n} where n refers to the number of halflives.
2) (n) = Number of Halflives = total time ¸ halflife of isotope
3) Original Mass = Final Mass x 2^{n} where n refers to the number of halflives
Example: What fraction remains of an original sample of I131 at the end of 32.28 days?
Halflife of I131 is 8.07 days. Therefore 4 halflives have occurred.
(1/2)^{n} = (1/2)^{4} = 1/16
Example: What is the halflife of an element that decays from 100g to 25g in 30 days?
100g®50g®25g = 2 halflives
Therefore one halflife equals 15 days
Example: If we start with 36 g of ^{42}K, how many grams will remain after 37.2 hours?
37.2 hours ¸ 12.4 hours = 3 halflives
36g®18g®9g®4.5g
Halflife problems
1. If you start with 75 g of P32, how many grams will be left after 42.9 days?
42.9 days ¸ 14.3 days = 3 halflives
75g®37.5g®18.75g®9.375g
2. After 4800 years, there is 2.0 g of Ra226 remaining. What was the original mass of the sample?
Original Mass = Final Mass x 2^{n}
4800 years ¸ 1600 years = 3 halflives
Original Mass = 2.0g x 2^{3} = 16g
3. A 40 gram sample of P33 decays to 10 grams in 50 days. What is the halflife of P33?
40g®20g®10g = 2 halflives
Therefore one half life equals 25 days
4. What fraction of C14 remains of a 1 gram sample after 17,190 years?
17190 years ¸ 5730 years = 3 halflives
Fraction Remaining = (1/2)^{n} = (1/2)^{3} = 1/8
Artificial Radioactivity
A) Artificial Transmutation: artificial radioactivity produced by bombarding the nuclei of stable atoms with high energy particles, thereby producing radioactive atoms
B) Fission Reactions: the splitting of an atomic nucleus into two smaller nuclei by bombardment of a neutron (Nuclear Bomb). *Nuclear Reactors are fission reactors.
Example: ^{235}_{92}U + ^{1}_{0}n ® ^{142}_{56}Ba + ^{191}_{36}Kr + 3(^{1}_{0}n) + Energy
C) Fusion Reactions: a nuclear reaction in which two or more light nuclei combine to form a single nucleus. Requires huge amounts of pressure and extremely high temperatures. Produces much more energy than fission. Occurs naturally on the sun. (Hbomb)
Example: ^{2}_{1}H + ^{2}_{1}H ® ^{4}_{2}He + Energy
Uses of Radioactive Isotopes:
A) Lab: to trace chemical reactions
B) Industry: Radiating food to preserve by killing bacteria, mold, insect eggs
C) Medicine: must have relatively short halflives and be quickly eliminated from the body.
1) I131 diagnosing and treating Thyroid conditions (halflife 8.07 days)
2) Co60 emits large amounts of gamma radiation as it decays, these rays can be aimed at cancerous tumors (halflife 5.26 years)
3) Ra226 used in treatment of certain cancers (halflife 1600 years)
4) Tc99 used in diagnosis of brain tumors (halflife 2.13x10^{5} years
D) Geology: 1)Fossils C14 to C12 ratio (while alive they are in equal amounts, once an organism dies C14 is no longer taken in)
2) Rocks U238 to Pb206 ratio (U238 decays through a series of steps until it forms stable Pb206. As time passes, the amount of U238 decreases while the amount of Pb206 increases).
Balancing Nuclear Equations
Steps for Balancing:
1) Due to the Law of the Conservation of Matter, whatever is on the left side of the equation must also be on the right side of the equation.
2) Add the mass numbers on the left side of the equation, this MUST equal the total mass numbers of the right side of the equation.
3) Add the atomic numbers on the left side of the equation, this MUST equal the total atomic numbers on the right side of the equation.
Example: ^{32}_{16}S + ^{1}_{0}n ® ^{1}_{1}H + ^{32}_{15}P
Write Your Questions Below

How can I tell which reactions are natural vs artificial? September 26, 2011 
 When you look at the reaction look for the particle type (alpha, gamma, beta, neutron, proton, positron). If it is on the reactant side of the equation, then it is artificial. If it is on the product side of the equation, then it is natural. Also if you look at Refence Table N (NYS Physical Setting/Chemistry Refence Tables) all of the reactions are natural transmutation. September 26, 2011  Replied By Expert 