Chemistry

1.12 - Development of the Periodic Table

1 min

note 1 of 1

The gaps Mendeleev left and his predictions

Mendeleev realised some elements hadn't been discovered yet, so he left gaps in his table rather than forcing elements into the wrong groups.
Each gap represented an undiscovered element.

Elements in the same group have similar properties that change steadily down the column.
Mendeleev used the elements on either side of a gap to predict the physical and chemical properties of the missing elements.
For example, he predicted the properties of ekasilicon, which closely matched the measured properties of germanium when it was later discovered.

When newly discovered elements matched Mendeleev's predictions, it proved his periodic table was a sound arrangement.

end of notes

Chemistry

1 min

note 1 of 1

Mendeleev realised some elements hadn't been discovered yet, so he left gaps in his table rather than forcing elements into the wrong groups.
Each gap represented an undiscovered element.

Elements in the same group have similar properties that change steadily down the column.
Mendeleev used the elements on either side of a gap to predict the physical and chemical properties of the missing elements.
For example, he predicted the properties of ekasilicon, which closely matched the measured properties of germanium when it was later discovered.

When newly discovered elements matched Mendeleev's predictions, it proved his periodic table was a sound arrangement.

end of notes