History of the periodic table
I can describe the development of the periodic table and explain its current form.
History of the periodic table
I can describe the development of the periodic table and explain its current form.
Lesson details
Key learning points
- Dalton (1803) arranged known elements in order of atomic weights.
- Newlands (1865) noticed that every eighth element, in order of atomic mass, repeated similar properties.
- Mendeleev swapped the order of atomic weights in order to fit elements better into groups of similar properties.
- Mendeleev’s periodic table had gaps and he predicted missing elements that were later found.
- Mendeleev was not aware of isotopes, so was unable to explain why the ordering by atomic weight was not always correct.
Common misconception
Pupils often believe that the when the periodic table was devised, scientists knew about the subatomic particles.
Emphasise when the subatomic particles were discovered in comparison to when Mendeleev devised his periodic table.
Keywords
Isotope - An atom of an element with the same number of protons, but different mass numbers due to different numbers of neutrons.
Atomic weight - The historical name for atomic mass, i.e. the ratio of the mass of an atom compared to a standard.
Relative atomic mass - The mean mass of an atom compared to 1/12 of the mass of a carbon–12 atom.
Dmitri Mendeleev - A scientist who devised the periodic table of elements.
Equipment
It is useful for students to have a copy of the periodic table.
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Video
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Starter quiz
6 Questions
vertical column in the periodic table
horizontal row in the periodic table
period 2
Group 1
period 3
Group 7
11 protons, 11 electrons and 12 neutrons
33 protons, 33 electrons and 42 neutrons
Group 2 and period 4
period 6 and Group 2
period 3 and Group 4
Group 0 and period 3
Exit quiz
6 Questions
only some similar elements were grouped together e.g. Li, Na and K
assumed all elements had been discovered
dissimilar elements were grouped together e.g. O, S and Fe
needed to double up elements to fit the repeating pattern