The elements of life

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The elements of life

• EL3
• Looking for patterns in elements

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Looking for patterns in elements

• When elements were being discovered, and more was
  being learned chemists looked for patterns in the
  information they had assembled
• We have seen close similarities between Ca and
  Sr, Magnesium (Mg) and Barium (Ba) can be added
  to make a group of four elements
• You probably know info about two other groups Gp
  1 (Li, Na, K) and Group7 (F, Cl, Br and I)

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Looking for patterns in elements

• 59 of the 92 naturally occurring elements had
  been discovered by 1850 the search for patterns
  in the elements were particularly fruitful around
  this time
• Much of the work was done by Johann Döbereiner
  and Lother Mayer in Germany, John Newlands in
  England and Dimitri Mendeleev in Russia

Döbereiner
Mendeleev
Newlands
Mayer
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Looking for patterns in elements- Newlands

• Reactions to their suggestions were not always
  favourable
• Some of the symbols look unfamiliar
• G is now Be
• Bo is now B
• Ro is now Rh
• By 1897 it had been established that Di was not
  an element, but a mixture of two closely related
  elements

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Looking for patterns in elements-Mendeleev

• 3 years after Newlands, Mendeleevs groupings
  were much more credible.
• Elements were arranged in order of increasing
  atomic masses, so that elements with similar
  properties came in the same vertical groups

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Looking for patterns in elements-Mendeleev

• Mendeleev left gaps in his table.
• Gaps were very important, they allowed the
  discovery of new elements
• Mendeleev made predictions about elements which
  had yet to be discovered.
• 1871, he predicted the properties of an element
  he called eka-silicon which he was confident that
  would be discovered to fill the gap between
  silicon and tin.

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Looking for patterns in elements-Mendeleev

• The element was discovered 15 years later and
  named germanium, its properties were almost
  exactly as he had predicted
• Since Mendeleev death in 1907, 8 elements have
  been discovered and 24 have been made in the lab

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Looking for patterns in elements-Mendeleev

• The first two elements to be made in the lab were
  neptunium (z 93) and plutonium (z94) these
  were made by bombarding uranium atoms with
  neutrons.
• By 1961 elements up to z 103 had been made
• By 2000 there were twelve more up to z 118

Glen Seaborg awarded the 1951 Nobel Prize in
Chemistry. He was co-discover of Plutonium and
lead the Manhattan Project's chemical process for
the separation, concentration and isolation of
plutonium
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Looking for patterns in elements

• The modern periodic table is based on the one
  originally drawn up by Mendeleev.
• It is one of the most amazingly compact stores of
  information ever produced!