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CHAPTER 11 (nuclear energy)
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32
Chemistry
Undergraduate 3
05/08/2012

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Term
isotope
Definition
an atom of an element differing in the number of neutrons in the nucleus but with the same number of protons & electrons
Term
radioactive decay
Definition
when unstable nuclei emit particles in the form of radiation
Term
radioisotope
Definition
an isotope of an element that undergoes radioactive decay
Term
background radiation
Definition
naturally occurring radiation from lots of things (from within our cells, from outer space "cosmic rays", radon, rocks & soil)

makes up ~82% of radiation we are exposed to
Term
synthetic radiation
Definition
non-natural radiation, comprises ~18% of the radiation we are exposed to

medical x-rays (11%), nuclear medicine, consumer products, occupational radiation, nuclear fuel cycle, other
Term
ionizing radiation
Definition
radiation with enough energy to knock electrons from atoms and molecules, converting them to ions

harmful effects can arise from the interaction of radiation and living tissue, as all living things operate on a balance

ex: nuclear radiation, x-rays
Term
radiation damaging cells
Definition
radiation-caused chemical changes in living cells can be highly disruptive

ionizing radiation can devastate living cells by interfering with their normal chemical processes

molecules can be splintered into reactive fragments called FREE RADICALS

(white blood cells and DNA are particularly vulnerable)
Term
nuclear equations
Definition
(differ from chemical equations because:)

nuclear equations rarely have the same elements on both sides of the arrow (as particles are often emitted, changing the protons and the element)

in nuclear equations we balance NUCLEONS (protons and neutrons) - we focus on balancing the atomic numbers (protons) and nucleon numbers in starting materials and products - MUST SPECIFY ISOTOPE

the number of nucleons in the starting material must equal the total number of nucleons in products - same is true for atomic numbers
Term
alpha decay
Definition
spontaneous breakdown process of radiation giving off alpha particles - which are identical to helium nuclei (2 neutrons, 2 protons, atomic number 2, nucleon number 4)

ALPHA PARTICLE:

mass of 4u, charge of +2, results in nucleon number decreasing by 4, atomic number decreasing by 2
Term
beta decay
Definition
radioactive breakdown process giving off beta particles - which are identical to electrons

a neutron within the nucleus is converted into a proton which remains and an electron (beta particle) which is ejected

the atomic number increases (1 neutron into 1 proton) but nucleon number remains the same

BETA PARTICLE:

mass of 0, charge of -1, no change in nucleon number, atomic number increases by 1
Term
gamma decay
Definition
radioactive breakdown process where gamma rays are emitted

gamma rays have NO MASS and NO CHARGE - neither the nucleon number nor atomic number change, just some energy is released

penetrating power of gamma rays is extremely high as they are so small and energetic - as a high energy photon moving at the speed of light

GAMMA RAY:

no mass, no charge, no change in nucleon number, no change in atomic number
Term
positron emission
Definition
radioactive decay process emitting a positron (identical to beta particle but positive in charge) and resulting in a decrease in atomic number of 1, and no change in nucleon number

a proton in the nucleus changes into a neutron and a positron, which is emitted

nucleus has 1 more neutron and 1 less proton, but nucleon number remains the same as total is the same

positrons emitted come in contact with electrons, are obliterated, and release 2 gamma rays

POSITRON:

mass of 0, charge of +1, no change in nucleon number, atomic number decreases by 1
Term
electron capture
Definition
radioactive decay process resulting in a decrease in atomic number of 1, and no change in nucleon number

nucleus absorbs an electron from an inner electron shell (1st or 2nd), energy is released in the form of X-rays as electron moves from shell to nucleus where electron joins with proton to form a neutron

electron is reactant on left side but NOT product on right - product is neutron added

nucleon number remains the same, atomic number decreases by 1

ELECTRON CAPTURE:

no mass, charge of -1, no change in nucleon number, atomic number decreases by 1
Term
half-life
Definition
time it takes for one half of the original number of atoms of a radioactive isotope to undergo radioactive decay

fraction remaining = 1/2^n
Term
common half-life dating techniques
Definition
carbon-14: useful for 500 - 50,000 years, organic material, half life 5730 years

hydrogen-3 (titrium): useful for 1-100 years, aged wines, half life 12.26 years

lead-210: useful 1-75 years, skeletal remains, half life 22 years

potassium-40: useful for 10,000-oldest Earth sample years, rocks, Earth's crust, moon's crust, half life 1.25x10^9 years

rhenium-187: useful for 4x10^7 years to oldest samples in universe, meteorites, half life 4.3x10^10 years

uranium-238: useful for 10^7 years-oldest Earth samples, rocks, earth's crust, half life 4.51x10^9 years
Term
transmutation
Definition
changing one element into another via altering the nucleus

(ARTIFICIAL TRANSMUTATION): brought on by bombardment of nucleus with alpha particles, neutrons, or other subatomic particles, resulting in radioactive emission
Term
Rutherford's artificial transmutation experiment
Definition
1919: bombarded a variety of light elements with alpha particles, resulting in production of protons

significance: he obtained protons from the NUCLEUS of an atom other than hydrogen, establishing proton's place in all nuclei - also was the FIRST example of artificial transmutation
Term
radioisotope tracers
Definition
used in physical, chemical, biological systems to detect decay products and track the movement through a system

isotopes of a given element behave nearly identically in chemical and physical processes, radioactive isotopes are easily detectable through decay products

(detect leaks in underground pipes, determine fictional wear in piston rings, determine the uptake of phosphorous and its distribution in plants)
Term
radioisotopes in agriculture
Definition
- used for inducing genetic mutations for the safety of a crop
- used for destroying microorganisms that cause food spoilage
Term
radioisotopes in medicine
Definition
- used for therapeutic reasons
- used for diagnostic reasons (obtaining information about the state of health)

radiation therapy - destroying cancerous cells, lethal to rapidly reproducing cells (cancer cells), concentrated beam to minimize exposure to healthy cells

- thyroid problems, brain problems, heart problems, seeing bone density, etc.
Term
penetrating power
Definition
- the more massive the particle, the less penetrating power
- the faster a particle moves or the more energetic the radiation, the more penetrating power

in order of most to least penetrating:
gamma rays, beta particles, alpha particles

alpha particles inside the body do lots of damage as they are bigger and don't move far
beta particles inside the body distribute little damage over a larger area - less concentrated damage, easier to recover
Term
fission
Definition
the release of nuclear energy by splitting heavy nuclei into smaller nuclei
Term
fusion
Definition
the release of nuclear energy by combining light nuclei to form heavier ones

source of sun's energy
Term
einstein's equation
Definition
e=mc^2

m=mass
e=energy
c=speed of light

mass and energy are just 2 different aspects of the same thing, and little bit of mass can yield enormous energy

a chemical reaction that gives off heat must lose mass in the process, but the change in mass is far too small to measure
Term
binding energy
Definition
(protons and neutrons combining to form atomic nuclei, and a small amount of mass is converted to energy) - this is the energy that holds the nucleons together in the nucleus

mass defect - missing mass between calculated mass of all particles in nucleus and actual measurement of nucleus

use einstein's equation to calculate binding energy using mass defect, figure out how much volts required to separate nucleus into constituents - more binding energy required, more stable
Term
chain reaction
Definition
the process by which nuclear fission can induce nuclear fission of other neighboring atoms and set off a whole group of atoms into fission (by means of bombardment)

Leo Szilard realized this, realized it could be made into a bomb
Term
Manhattan Project
Definition
a secret research project in 1939 on the study of atomic energy, launched by President Roosevelt, in order to construct a bomb using uranium, plutonium, graphite (to slow reactions and increase likelihood that chain would happen) and chain reactions
Term
critical mass
Definition
amount of whatever in a bomb needed to sustain the fission reaction all the way through
Term
radioactive fallout
Definition
when a nuclear explosion occurs in the open atmosphere, radioactive materials can rain down on parts of Earth thousands of miles away, days and weeks later

it is very complex, with the most dangerous isotope being strontium-90 (similar to calcium, gets incorporated into bones, source of internal radiation)
Term
difference between power plant and bomb
Definition
power plant employs use of slow, controlled release of energy from a nuclear chain reaction (with less enriched uranium), rather than all at once explosion
Term
advantages and disadvantages of nuclear power
Definition
ADVANTAGES:

reduced CO2 emissions
lower volume of waste than coal/natural gas
lower fuel costs
1/5 the annual occupational health deaths than coal
huge reserves of uranium and thorium - reliable
nuclear power plants operate at industry's highest efficiency percent

DISADVANTAGES:

spent fuel handling and waste storage problems for potential land contamination and broad-scale lethal exposure
potential to be used for deadly weapons
costs a lot to build a power plant
Term
thermonuclear reaction
Definition
reactions that take place in the sun - requiring enormously high temperatures (millions of degrees) to initiate - causing nuclei to fuse and release unimaginable amounts of energy (fusion)

principal reaction of sun:
fusion of 4 hydrogen nuclei to produce 1 helium nucleus and 2 positrons
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