Chemistry Chapter 4: The Periodic Table

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Chemistry Chapter 4 The Periodic Table

• Section 4 FromWhere Did the Elements Come?

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Key Terms

• Nuclear reaction reaction that affects atomic
  nucleus
• Superheavy element an element with an atomic
  gt 106
• Transmutation changing from one element to
  another

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Key Terms 2

• Emc2 Ensteins quantitative description of the
  mass energy-relationship
• Here e, m and c are energy, mass the speed of
  light, respectively.

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Key Terms 3

• Supernova explosion of stars more than 100x
  more massive than the sun
• The blast is caused by conversion of core H He
  into elements up to Fe.
• During the explosion, this change yields collapse
  formation of ele-ments with higher atomic
  than Fe.

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Key Terms 4

• Synthetic elements created by chemists using
  particle accelerators, these elements do not
  occur naturally and have atomic gt 92.
• Cyclotron charged particle acceler-ator 1st
  invented by the American sci-entist E.O. Lawrence
  in 1930

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Key Terms 5

• Synchrotron used to create superheavy elements
• This device accelerates a few types of charged
  particles past 1/10th the speed of light, c.
• One tenth c is the top speed that cyclotrons can
  yield.

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Things To Know/Answer

• How do the naturally occurring elements form?
• How does a transmutation change one element into
  another?
• How are particle accelerators used to create
  synthetic elements?

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Natural Elements

• Only 93 of the elements in the periodic table are
  found in nature.
• Technetium,Tc promethium, Pm, neptunium, Np,
  are found in the spectra of stars.
• C, H, O, N, P S are most of the atoms in living
  things.

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Natural Elements 2

• Popular theory common and natural elements were
  created in the centers of stars billions of years
  ago, shortly after the Big Bang
• H He formed after the Big Bang through cooling
  of temperatures.

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Natural Elements 3

• Here, energy was able to become subatomic
  particles.
• These formed H He in clouds that gravity
  centralized.
• The cloud gathering yielded great solar density
  which caused rising central temperature
  pressure.

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Natural Elements 4

• Nuclear reactions started in these solar centers.
• Stars have fusion reactions where 4H become 1He
  with an apparent loss of mass that becomes
  energy.
• Emc2 describes this change.

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Natural Elements 5

• Other elements can form by fusion. See Figure 28
  on pg. 144.
• See www.scilinks.org Origin of Elements under
  code HW4093.

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Transmutations

• Middle Ages alchemists trying to turn Pb into
  Au via ordinary or non nuclear chemical
  reactions.
• Were they successful? See Alchemy at code HW4006.

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Transmutations 2

• Rutherford saw particle tracks in his
  experiments.
• He reasoned that they came from disintegration of
  atomic nuclei after being struck by a-particles.

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Transmutations 3

• W.D. Harkins, an American, P.M.S. Blackett
  confirmed that Y shaped tracks meant
  transmutation
• This was b/c N disintegrated into O and a proton
  when struck by an a-particle.

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Synthetic Elements

• Researchers hopped on the transmuting train
  synthesized elements that were not available in
  nature w/ particle accelerators.
• Cyclotrons Synchrotrons use successive pulses
  of energy to speed up charged particles.

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Synthetic Elements 2

• They make particles collide at high speed and
  energy, fuse, and form heavier elements.
• Greater speed yields greater mass and more
  difficulty continuing acceleration

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Synthetic Elements 3

• The charge particles must reach successive pulses
  on time.
• If not, they slow down, lose energy and fail to
  fuse.
• Most superheavy elements last for a small
  fraction of a s except for 114.

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Synthetic Elements 4

• The only time scientists synthe-sized element
  114, it lasted for 30s then decayed to 112. Why
  is this problematic?
• Russian scientists bombarded Pu-214 with Ca-40
  for 40 days to create 114.

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Synthetic Elements 5

• Many researchers view element 114 as the
  beginning of a stable set of synthetic elements.
  Why?