Alchemy%20Unit

1
Alchemy Unit

• Investigation IV Subatomic World

Lesson 1 Island of Stability
Lesson 2 Its Greek to Me
Lesson 3 ELEMENTary Education
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Alchemy Unit Investigation IV

• Lesson 1
• Island of Stability

3
ChemCatalyst

• The isotope notation for an atom of copper and an
  atom of gold are given below.
• How could you change a copper atom into a gold
  atom?
• What would you need to change? Give specific
  numbers.
• Why is this change called a nuclear reaction?

4
The Big Question

• What is the range of the number of neutrons found
  in isotopes of various elements?

5
You will be able to

• Determine how many neutrons are required to make
  a stable element with a given number of protons.

6

Notes

• Nuclear chemistry is the study of the nucleus of
  the atom.
• The band of stability is the range in the number
  of neutrons for a given number of protons for
  isotopes that are found in nature.

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Activity

• Purpose Some combinations of neutrons,
  electrons, and protons are not stable enough to
  be called elements. This lesson shows you how to
  predict the numbers of neutrons, electrons, and
  protons of the isotopes they are likely to find
  in nature.

(cont.)
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(cont.)
(cont.)
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Making Sense

• What kind of generalization can you make about
  how the number of protons and neutrons are
  related to each other in the elements?

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Notes

• Radioactive elements are less stable because the
  isotope is lost over time as pieces of the
  nucleus spontaneously emerge.
• The concept of isotope stability is highly
  dependent on time. Atoms that exist for a long
  time are referred to as stable. Radioactive atoms
  disappear over time and are referred to as
  unstable.

(cont.)
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(cont.)

• Any isotope that is around long enough to be
  detected and measured qualifies as an element,
  but still can be highly unstable and radioactive.

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Check-In

• Use your graph to determine how many neutrons you
  would need to make a stable element with 75
  protons.
• How many neutrons would make a radioactive
  element with 75 protons?

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Wrap-Up

• In order for an atom to be considered an element,
  it has to have a stable nucleus and exist long
  enough to be detected.
• The neutron to proton ratio is an important
  factor in determining the stability of a nucleus.
  
• Some isotopes are more stable than others.
  Unstable isotopes undergo nuclear decay to
  produce atoms with lower mass.

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Alchemy Unit Investigation IV

• Lesson 2
• Its Greek to Me

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ChemCatalyst

• Uranium-238 is used in nuclear reactors to
  generate electricity. In the nuclear reactor,
  uranium-238 changes to lead-209.
• How can atoms of uranium-238 change into atoms of
  lead-209?
• The nuclear reaction is initiated by colliding
  the uranium-238 with . What do you think
  this symbol represents?

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The Big Question

• What changes in the nucleus during radioactive
  decay?

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You will be able to

• Predict the result of radioactive decay of an
  atom.

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Notes

• A nuclear reaction happens when the nucleus of an
  atom is unstable and spontaneously decays
  emitting particles.
• There are two types of nuclear decay, alpha and
  beta. Depending on the type of decay either an
  alpha particle or beta particle is emitted.

(cont.)
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(cont.)

• Chemists use equations like the following one to
  represent nuclear reactions.

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Activity

• Purpose This activity introduces you to two
  common forms of nuclear decay.

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Making Sense

• Give a specific example of how a chemist might
  make gold using alpha decay. Be specific about
  which isotope of gold is made.
• Give a specific example of how a chemist might
  make gold using beta decay. Be specific about
  which isotope of gold is made.
• Would the isotopes of gold prepared by alpha and
  beta decay be located in the band of stability?

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Notes

• Alpha decay and beta decay are two forms of
  radiation or nuclear decay.
• During alpha decay a nucleus is splitting into
  two smaller elements, one of which is always a
  helium atom.
• Chemists use the symbol (the Greek letter alpha)
  to represent an alpha particle.

(cont.)
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(cont.)

• During beta decay a neutron inside the nucleus of
  an atom emits an electron. This electron is a
  part of nuclear decay and therefore comes from
  the nucleus.
• Under certain circumstances each neutron can be
  further split up into an electron and a proton.
• Removal of an electron from a neutron alters the
  neutron so that it becomes a proton.

(cont.)
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(cont.)

• The process of splitting a large nucleus into
  smaller ones is called nuclear fission.
• Besides alpha and beta particles, many
  radioactive nuclei release energy in the form of
  gamma rays (? rays).

(cont.)
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(cont.)

• The release of a gamma ray causes no change to
  either the mass number or the atomic number of an
  atom because a gamma ray has no mass.
• Gamma radiation by itself does not change the
  identity of the atom. However, gamma ray emission
  usually occurs whenever there is alpha or beta
  emission.

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Check-In

• What products do you expect if an atom of
  actinium-227 undergoes alpha decay?

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Wrap-Up

• When changes occur in the nucleus of an atom it
  is called a nuclear reaction.
• When an alpha particle is emitted from an atom,
  the nucleus loses two protons and two neutrons.
  An alpha particle is the same as a helium atom.
• When a beta particle is emitted from an atom, the
  nucleus gains a proton and loses a neutron. A
  beta particle is the same as an electron.

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Alchemy Unit Investigation IV

• Lesson 3
• ELEMENTary Education

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ChemCatalyst

• The periodic table lists every element after
  uranium, U, as human-made elements.
• How are elements made in nature and by scientists?

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The Big Question

• How are elements formed?

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You will be able to

• Explain what it would take to turn one element
  into another.

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Activity

• Purpose The goal of this lesson is to examine
  the formation of the elements.

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Making Sense

• Why are the small owls breaking out their digging
  tools at the end of the comic strip?

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Notes

• The process of element formation is called
  nucleosynthesis.
• Nuclear fusion is a process that produces bigger
  elements from smaller ones. It requires
  extraordinarily high temperatures. At such high
  temperatures, nuclei are moving so fast that
  collisions between them can overcome the natural
  repulsion of their positive charges.

(cont.)
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(cont.)

• Heavier elements do not burst into fiery fusion
  by combination with ?-particles. They are formed
  by neutron capture followed by beta decay, among
  other processes. Nuclei add neutrons until one is
  converted into a proton and an electron (beta
  decay). A new element is formed because the
  atomic number increases by one. This happens in
  supernova explosions.

(cont.)
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(cont.)

• Chemical reactions are ones in which atoms remain
  unchanged.

• Revised definition of an element Stable elements
  cannot be broken apart into new elements in
  chemical reactions. It is possible to convert one
  element into another in nuclear reactions, but
  this requires a lot of energy for stable
  elements. Unstable elements undergo radioactive
  decay, and are broken apart spontaneously.

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Check-In

• Consider the chemical reaction between hydrogen
  and oxygen to form water.
• H2 2O2 ? 2H2O
• Name two ways in which a chemical reaction is
  different from a nuclear reaction.

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Wrap-Up

• Elements are converted from one to another in
  nuclear reactions, but not in chemical reactions.
• Nuclear reactions involve the energy of a
  supernova.