nuclear chemistry. isotopes when an atom or element can be found somewhere on earth, it is called...
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![Page 1: Nuclear Chemistry. Isotopes When an atom or element can be found somewhere on Earth, it is called naturally occurring. Of the 118 elements on the](https://reader035.vdocuments.us/reader035/viewer/2022062313/56649d0e5503460f949e3b19/html5/thumbnails/1.jpg)
Nuclear Chemistry
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Isotopes
When an atom or element can be found somewhere on Earth, it is called naturally occurring.
Of the 118 elements on the periodic table, 92 are naturally occurring; the rest exist only as a result of human activity or unusual circumstances.
Some elements have only one isotope, but most have more than one.
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Stable vs. Radioactive IsotopesRadioactive Isotopes
Not stable
Emit small particles (neutrons, protons, electrons, and odd mixes or variations of these particles).
Called radioactive isotopes.
not common; the majority of radioactive isotopes are elements with atomic numbers above 80.
Stable isotopes
have a stable nucleus. Stable = balance between the
number of protons and neutrons in a nucleus
Too few or too many neutrons will lead to the disintegration of an atom.
The larger the atom, the more neutrons it takes to make a stable nucleus.
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What is radiation????
Why are some substances radioactive?
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Nuclear Chemistry
Radiation: particles emitted from the nucleus
Substances are radioactive because the neutron to proton ratio is “off”
Radioactive substances emit radiation in order to get at n0: p+ ratio that is stable (low energy)
Band of Stability
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Nuclear Radiation
Radioactivity: particles or radiation emitted from a nucleus during radioactive decay
Radioactive Decay: the spontaneous break-down of a nucleus into a slightly lighter nucleus, accompanied by the emission of nuclear radiation
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Types of Nuclear Radiation
1. alpha particles
2. beta particles
3. gamma rays
Ionizing Radiation: can ionize atoms that they hit
Emission of these types of particles (nuclear reactions) involve changes to the nucleus of the atom!
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Alpha Radiation (α)
2 protons & 2 neutrons bound together.
Nucleus of a helium atom
Symbol 42He
Particles do not travel far and are not very penetrating
Particles can be stopped by a piece of paper!
U238 92 Th + He234
90 4 2
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Beta Radiation (β) An electron that has been ejected from the
nucleus Formed when a neutron breaks down into a
proton and electron Has a charge of -1 Mass 1/1837 amu
Symbol: 0-1e or β
Can pass through paper,
but not aluminum foil
or wood
C N + e14 6
0 -1
14 7
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Gamma Radiation (γ) high-energy photon emitted by a radioisotope is
a gamma ray (). often emitted along with alpha or beta particles
during radioactive decay. have no mass and no electrical charge. extremely penetrating; can be stopped, although
not completely, by several centimeters of lead.
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In your notebook.....
1. Sketch the picture below
2. Identify the type of radiation being depicted.
AB
C
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In your notebook.....
1. Sketch the picture below
2. Identify the type of radiation being depicted.
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Balancing Nuclear Equations
- follows law of Conservation of Mass
-mass numbers for products and reactants have to equal.
-atomic numbers for products and reactants have to equal.
37+0 = 37
20+ -1 = 19
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Balance the following nuclear equations by adding the correct particle, and complete the sentence
(copy these into your notebook!)
Uranium-235 undergoes _____________ decay
Radium 226 undergoes _____________ decay
Technecium-99 undergoes _____________ decay
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Writing nuclear equations
Write a balanced nuclear reaction for the following:
1. Potassium-37 undergoes beta decay.
2. Polonium-210 undergoes alpha decay.
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Half LifeIs the time required for one-half of a sample to decay (really, to change
into another element).
For example, it takes 5730 years for half of a sample of carbon-14 to decay into nitrogen-14 through beta decay.
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Calculate Half Life
AF = AI * (.5) t/h
Final Amount Initial
Amount
Time
Half-Life
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Give it a try
An isotope of cesium (cesium-137) has a half-life of 30 years. If 1.0 mg of cesium-137 disintegrates over a period of 90 years, how many mg of cesium-137 would remain?
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Fission & Fusion
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Fusion
Fusion: when two small nuclei combine to form a larger more stable nucleus
Ex.: energy from the sun comes from nuclear fusion
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Fission
Fission: a large nucleus splits apart into lighter more stable nuclei
Ex.: type of reaction that occurs in a nuclear reactor