nuclear notes: structureandradioactivity online @ redwood.org/stewart

Nuclear Notes: Nuclear Notes:

StructureStructure

andand

RadioactivityRadioactivity

Online @ Online @ redwood.org/stewartredwood.org/stewart

I. Structure of the AtomI. Structure of the Atom

RecognizeRecognize

Me?Me?

Draw

Me!

II. Periodic TableII. Periodic TableAtomic # vs. Atomic Mass Atomic # vs. Atomic Mass

A. Atomic No. - number of protons in the nucleus

B. Atomic mass - the sum of the mass of protons, neutrons, and electrons.

1. no. of neutrons = atomic mass - atomic no.

2. no. of neutrons is not always the same!

isotopes - atoms of the same element (same number of protons) that have different number of neutrons

III. RadioactivityIII. Radioactivity

A.A. The activity of unstable The activity of unstable isotopesisotopes (radioisotopes). (radioisotopes). Isotopes and large atoms are unstable and will break apart.

B.B. Nucleus is Nucleus is decomposingdecomposing, defined as losing mass/particles, and/or , defined as losing mass/particles, and/or energyenergy

C.C. Decomposition continues until enough mass has been lost making Decomposition continues until enough mass has been lost making the atom stable again. the atom stable again. New, lighter atoms are formed, releasing radiation in the process.

a.k.a. radiationa.k.a. radiationThe emission of particles due to the breakdown of atomic nuclei

ThereforeThereforeThereforeTherefore Unstable = radioactiveUnstable = radioactive

IV. Types of RadiationIV. Types of RadiationThese 3 types of radiation are all naturally-occurring.These 3 types of radiation are all naturally-occurring.

A.A. Alpha Alpha (()) particle (Helium atom):particle (Helium atom):1. charge of +21. charge of +2

2. mass of 42. mass of 43. 3. The atomic # of the decaying atom decreasesby 2 and the mass decreases by 44. 4. Effective shielding materials include paper and dead skin

SymbolSymbol

Sum of mass numbers (p + n) and sum of atomic numbers (p) is the SAME on both sides of equation.

B.B. Beta ( Beta ( ) ) particle (electron): particle (electron):1. negatively charged: charge of -1 [otherwise known as an electron (1. negatively charged: charge of -1 [otherwise known as an electron (e--)])]

2. no measurable mass2. no measurable mass3. this type of decay/radiation occurs when one 3. this type of decay/radiation occurs when one neutronneutron is converted to a is converted to a protonproton, thus increasing the atomic number by 1., thus increasing the atomic number by 1.

4. 4. The atomic # of the decaying atom increases by 1and the mass does not change. Effective shielding materials include plastic, glass and aluminum

SymbolSymbol


C.C. Gamma ( Gamma ( )) radiation: radiation:1. high energy photon1. high energy photon

2. powerful and dangerous2. powerful and dangerouscan penetrate 3-4 cm of leadcan penetrate 3-4 cm of lead

4. virtually all nuclear reactions have this (including naturally and non-4. virtually all nuclear reactions have this (including naturally and non-naturally occurring reactions)naturally occurring reactions)5. no measurable mass, no charge 5. no measurable mass, no charge no change in massno change in mass

The atomic number and mass of the decaying atom do not change. Effective shielding materials include thick lead and concrete

SymbolSymbol


Where does the gamma radiation come from? Mass is converted into energy (more on this later).

Radiation Summary Slide

V. Nuclear FissionV. Nuclear FissionA. The nuclear reaction the world currently uses to generate any

and all usable nuclear energy--not naturally occurring.

B. Fission: the splitting of a large atom into smaller fragments (particles and/or smaller atoms)

C. A large atom is struck by a single neutron. Smaller atoms are created. Energy and neutrons are released

D. The most common large atom used:

Uranium (U) - 235 *** atomic number 92

Ques? How many neutrons does U-235 have?

Answer: 235 - 92 = 143


VI. Nuclear FusionVI. Nuclear Fusion

A. Fusion: the combining of 2 smaller atoms into a larger atom--not naturally occurring on earth.

B. Only possible with isotopes of Hydrogen.

Trit

HeNeutron

Nuclear Energy Summary Diagram

VII. Where does the kinetic energy in a nuclear reaction come from?

• The mass of protons and neutrons varies depending on what atom they are in. The mass of protons and neutrons before a nuclear reaction is GREATER than after the reaction.

Fission

Fusion

VII. Where does the kinetic energy in a nuclear reaction come from?

• The mass is TRANSFORMED into kinetic energy according to Einstein’s famous equation:

• E = mc2 -- mass IS energy!• Energy equals mass times the speed of light

squared. The speed of light is 300,000 kilometers per second, so even a very small mass produces a LOT of energy !

VIII. Energy EvolvedVIII. Energy Evolved

A.A. FISSIONFISSION: 1 gram of U-235 evolves 2x10: 1 gram of U-235 evolves 2x1077 Cal/g Cal/g ((20 million Cal/g20 million Cal/g))**

** which equals the heat from 30 tons of TNT which equals the heat from 30 tons of TNT

VersusVersus 1 gram of oil = 9.8 Cal1 gram of oil = 9.8 Cal

1 gram of Uranium = 20,000,000 Cal1 gram of Uranium = 20,000,000 Cal

B. The energy released in nuclear B. The energy released in nuclear FUSIONFUSION is about is about 7 7 timestimes greatergreater than the energy released in the fission of than the energy released in the fission of Uranium. Uranium. 10 grams of Deuterium which can be extracted from 500 liters of water could produce enough fuel for the lifetime electricity needs of an average person in an industrialized country.

VII. Advantages and Disadvantages of Using Nuclear Fuel

A. Advantages:

• Fuels are plentiful.

• If shielded properly, it is inherently safe since any malfunction results in a rapid shutdown.

• No atmospheric pollution leading to acid rain or global warming.

• Small amounts of mass yield high amounts of energy.

B. Disadvantages:

• What are some disadvantages of using Nuclear Fuel to generate electricity?

nuclear notes: structureandradioactivity online @ redwood.org/stewart

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