Download Chapter 9: Nuclear Chemistry

Chapter 9 Notes
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Chapter 25: Nuclear Chemistry
I.
Atomic Number, mass number and isotopes
A. Atomic number: number of _________ in the _________. The
atomic # determines which _____________ an atom is.
B. Mass number: Sum of the ____________ and ___________ in the
nucleus. This is also shown on the ___________________, but that
number is an ______________, which is ________________ (can’t
have a decimal of proton + neutron).
Symbol:
C. Isotopes: Atoms with the same ___________ # (__________), but
different _________ numbers (# of _____________ is different).
 Named as: Element symbol – Mass Number
(Uranium-238)
 There are about 1500 known isotopes of all the elements. Only about
264 of these are stable. The rest have unstable nuclei and are
radioactive. These unstable nuclei will undergo radioactive decay in
order to become stable.
II.
Radiation: Energy that is emitted from a ________ and travels
through__________. Examples:
____________________________.
 Ionizing radiation has enough ________ to change atoms and
molecules it strikes into ________. Includes _______________
______________________.
III.
Radioactivity: The spontaneous emission of ____________ and
(sometimes) particles from the ______________ of an unstable atom.
Emissions from such nuclei can be one of three types:
Chapter 9 Notes
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A. Alpha ( ) emission: particles that consist of _____________ and
______________ (like a _________ atom without the electrons.)
________________ charged. Emitted at about _________the speed
of light. _____________, but the ____________ penetrating.
Symbol:
B. Beta ( ) emission” particles that are _____________ emitted at
_________ the speed of light. _______________ charged.
________ penetrating than alpha particles. There are also ______
particles (_______________) that are identical to electrons but have a
____ charge.
Symbols:
C. Gamma ( ) emission: Pure _____________________
energy; more energetic than _____________. Travels at the speed of
light. Has no _________ or _________. The most penetrating.
IV.
Nuclear Equations
A. In nuclear equations, the sum of the ___________________ on the
left side of the arrow must equal the sum of the _________________
on the right. Same rules apply to the atomic numbers.
B. Example:  decay of U-238
C. Example:  decay of Mg-27 (both positron and electron)
D. Sometimes _______ is lost and turned into _________(conflicts with
the Law of conservation of mass)
1. Einstein’s equation:
Where E =
m=
c=
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2. Example: Example: How much energy (in KJ) is released when 1
mole of oxygen-14 decays by β+ (positron) emission to form
nitrogen-14? The masses are:
oxygen-14 = 14.0086 g
β+ (positron) = 0.0005 g
nitrogen-14 = 14.0031 g
V.
Half Life (
)
A. The amount of time it takes for _________ of a sample of a radioactive
nuclide to ___________. A half life can be a fraction of a second or
thousands of years, depending on which nuclide is decaying. As each half
life passes, the amount of nuclide remaining undecayed decreases by
______________. The half-life for carbon is ___________ years.
B. To determine how much of a nuclide remains undecayed after a certain
number ( ) of half-lives has passes:
C. Example problem: Fluorine-21 has a half-life of approximately 5 seconds.
What fraction of the original nuclei would remain after 1 minute? If you
began with 21 grams, how many grams would remain?
VI.
Fission and Fusion
A. Nuclear fission: “_________________________” Certain nuclei will
break into __________________________, which releases large
amounts of __________. The energy is due to the “_____________”,
or the tiny amount of ________ that has been converted to energy.
Calculated with __________.
Chapter 9 Notes
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*A tiny amount of mass converted to energy will result in a very large amount of
energy. The atomic bomb utilized an uncontrolled fission chain reaction. Modern
nuclear reactors (like the San Onofre plant) a controlled chain reaction as a source of
heat to generate steam to turn turbines to generate electricity.
1.
Chain Reactions
a. The continuous bombardment of the same radioactive isotope
with ___________.
b. The unstable nucleus that absorbed the neutrons _________,
forming ___ nuclei and the emission of more___________.
2.
Size does matter.
a. Sometimes the neutrons will not be absorbed by the material
because of the ___________________ of the nucleus.
b. The probability of hitting the nucleus is ____________ as the
size of the nucleus ____________. The smallest size the
nucleus can be to keep the chain reaction going is called the
____________________. The accident at Chernobyl was a
result of a runaway fission reaction.
c. Chernobyl:
B. Nuclear Fusion: Energy is released as small nuclei ____________
_______________ to form a ________________ nuclei.
C. In stars, including our _______, ____________ is converted to
____________.
Reaction: