Development of the Periodic Table Flashcards
How were elements first ordered by?
Atomic weight.
Who proposed the ‘law of octaves’, and in what year?
Newlands, in 1864.
What did Newland base his order on?
- He ordered them by atomic weight.
- He said the properties of every eighth element were similar.
What problem did Newland face?
New elements were being discovered which did not fit into his table.
Who slightly changed the order and left gaps, and in what year?
Mendeleev, in 1869.
What did Mendeleev use his table to do?
-He predicted the properties of undiscovered elements.
Why was his table accepted?
Newly discovered elements had similar properties to the ones which he predicted.
How are elements ordered in the modern periodic table?
By atomic (proton) number.
What is the same about all elements in a group?
They have the same number of electrons on the outer shell - the highest energy level.
