Chemistry 105
You need:
Text & Lab Book (+ all lab safety stuff)
Online Notes access:
http://learn.roguecc.edu/science/ploozen/
Nuclear Chemistry
Is this what the Alchemists really were looking for?
Isotopes/Nuclides
An isotope is an atom of an element with a specific atomic number and a
different mass number than another isotope of that element.
Carbon-12 and Carbon-14 are isotopes of the same element.
Stable vs. Unstable isotopes
Radioactivity
Radioisotope
Radioactivity
Several types of radiation can be spontaneously emitted from unstable isotopes.
Ernest Rutherford discovered that naturally radioactive materials emitted three
types of radiation:
Alpha - Positive component; particles which are composed of 2 protons
and 2 neutrons
Beta - Negative component; particles with charge and mass identical to
that of an electron (the antiparticle of a  particle is a positron – same
mass, but opposite charge)
Gamma - Uncharged component; high energy radiation without mass.
Nuclear Reactions: Radioactive Decay
Process whereby a radionuclide is transformed into a nuclide of another element
as a result of radiation emission.
Parent nuclide --> Daughter nuclide + radiation
The sum of A and the sum of Z must be the same on both sides of a
nuclear equation.
Nuclear equations can be written expressing this process
Alpha emission
U-238  Th-234 + 
Beta emission
Th-234  Pa-234 + 
Positron emission
F-18  O-18 + +
*Gamma emission
Ra-226  Rn-222 + 
Decay series: many radionuclides decay in a series of steps until a stable nucleus is
formed
Decay Series for Uranium-238
In the U-238 decay series, each nuclide is unstable except Pb-206.
Rate of Radioactive Decay
Decay rates are measured using the concept of Half-Life.
A half -life (t1/2) is the time required for one-half of a given quantity of a
radioactive substance to undergo decay!
Calculations
(
) (
) ( )
This calculation allows you to determine the amounts of radioactive material that
has decayed, the amount that remains undecayed and the time elapsed for the
decay process!
Example
The half-life of iodine-131 is 8.0 days. How much of a 0.16 g sample of iodine131 will remain undecayed after a period of 32 days?
Example
Strontium-90 has a half-life of 28.0 years. How long will it take for 94% (15/16)
of the strontium-90 atoms to undergo decay?
Transmutation
Transmutation is the process of atoms of unstable nuclide A changing into atoms
of nuclide B.
This can occur naturally (by radioactive decay) or...
...as a result of bombardment reactions
Example: Bombardment of nitrogen-14 with alpha particles... oxygen-17 was
formed.
Bombardment Reactions
The production of synthetic elements (transuranium elements) and non-natural
nuclides of other elements are the result of bombardment reactions.
Example
208
Bi + 4He --> 210At
Chemical Effects of Radiation
Radiations produced from radioactive decay can interact with atoms and
molecules of surrounding material.
Electrons of these atoms/molecules are most directly affected by radiation.
Excitation
Ionization
Types of radiation:
Nonionizing - excitation (low energy)
Ionizing (high energy) - resulting in formation of ion pairs
Free Radical Formation
Free radical: atom, molecule or ion containing an unpaired electron
Free radicals rapidly react with nearby chemicals.
Stable molecule
Another free radical
Example:
H2O + radiation --> H2O+ + eH2O+ + H2O --> H3O+ + OH
(hydroxyl)
Effects on the Human Body
Biochemical Effects of Radiation
Alpha - due to ingestion
Example: polonium-210
Beta - both internal and external
Example: skinburns
Gamma - this is very effective!!
Radiation Detection
Filters
Example: Film badges used in nuclear power facilities
Geiger counters
Contain gas atoms that are ionized...
Sources of Radiation
Natural
Radon seepage, rocks & soils, minerals in the body, cosmic radiation.
Human-made
Medical X-rays, nuclear medicine, consumer products, occupational
exposure, nuclear fallout (from weapons testing and nuclear power plants)
Cells that reproduce rapidly are most sensitive to radiation damage.
Nuclear Medicine
Diagnostic uses: use a radionuclide of an element already present in the body
The movement of the radionuclide is easily monitored.
Therapeutic Uses: used to selectively destroy abnormal cells
Fission & Fusion reactions
Fission: a large nucleus splits into two medium-sized nuclei with the release of
several free neutrons and LOTS of energy.
Fusion: two small nuclei are collided together to produce a larger nucleus and
LOTS of energy.
Fission
Uranium-235 undergoes fission when a neutron collides with the nuclide.
If enough radionuclides are present, a “chain reaction” can occur. Watch out!
Fusion
Naturally occurs in stars!
Comparing Chemical & Nuclear Reactions