Development of the periodic table
- Created by: Sophie Zhang
- Created on: 01-03-18 19:10
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- Development of the Periodic Table
- Early 1800s
- John Dalton
- Arranged elements in order of atomic mass
- John Dalton
- 1864
- John Newlands
- Noticed that every eighth element seemed similar
- He assumed all the elements had been found
- Did not take into account that scientists were still discovering new ones
- He assumed all the elements had been found
- 'Law of Octaves'
- Only worked for the known elements up to Calcium
- Some scientists ridiculed his ideas and refused to accept them
- Noticed that every eighth element seemed similar
- John Newlands
- 1869
- Dmitri Mendeleev
- Placed them in order of atomic mass
- He arranged them so that a periodic pattern in their properties could be seen
- Left gaps for undiscovered elements
- Used his table to predict the properties of elements that were yet to be discovered
- Not all elements fit in with his pattern
- e.g. Argon (noble gas) and Potassium (very reactive metal)
- Argon atoms have a larger relative atomic mass than potassium
- Following Mendeleevs rule, argon was in the same group as reactive metals such as sodium and lithium
- Potassium would be in a group with the noble gases
- Simply changed the order so that elements with similar properties could be in the same group
- Argon atoms have a larger relative atomic mass than potassium
- e.g. Argon (noble gas) and Potassium (very reactive metal)
- Placed them in order of atomic mass
- Around 50 elements had been identified
- Dmitri Mendeleev
- Early 1900s
- Solved the issue of elements breaking the periodic pattern
- In order of number of protons (atomic number)
- Existence of isotopes
- Solved the issue of elements breaking the periodic pattern
- Early 1800s
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