What did scientists in the 1800s have no idea about, but what could they do?
In the 1800s, scientists had no idea about the structure of atoms, but they could measure the relative atomic mass of each element.
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What did scientists begin to notice when all the elements were put in order of their relative atomic mass?
Periodic patterns in the properties of the elements.
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When or who arranged 50 or so know elements and according to what, and to make what?
In 1869, Russian scientist Dmitri Mendeleev arranged 50 or so known elements according to their properties and the properties of their compounds to make a Table of Elements.
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What did Mendeleev's table place?
Mendeleev's table placed elements with similar chemical properties in the same vertical groups - but he found that he had to leave gaps in his table to make this work.
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Describe about the gaps.
The gaps in Mendeleev's table of elements were really clever because they predicted the properties of undiscovered elements.
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What has happened since with the gaps?
New elements have been found which fit into the gaps left in Mendeleev's table (e.g, scandium, gallium and germanium)
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What sort of group has been discovered and added? Describe the properties.
A whole new group of elements has been discovered and added to the table. This group includes helium, neon and argon. These are colourless gases that don't react with much at all. (which is why no one knew about them in Mendeleev's day).
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What has happened over the last hundred years or so?
The table has been refined to produce the periodic table.
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Other cards in this set
Card 2
Front
What did scientists begin to notice when all the elements were put in order of their relative atomic mass?
Back
Periodic patterns in the properties of the elements.
Card 3
Front
When or who arranged 50 or so know elements and according to what, and to make what?
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