development of the periodic table Flashcards
what were elements arranged by in the 1800s?
atomic weight
who came up with their own table of the elements in 1869?
dimitri mendeleev
how did mendeleev arrange his table?
mostly in order of atomic weight, but switched elements if the properties meant it should be changed
why did mendeleev leave gaps?
for elements he thought hadn’t been discovered yet
what did newly discovered elements help to confirm?
that Mendeleev was correct as they fitted the pattern
what helped explain why the order of atomic weight was incorrect?
isotopes
describe the early periodic tables
incomplete with some elements placed in incorrect groups
similarities between newlands and mendeleevs table
-both arranged in order of atomic weight
how did newlands arrange the elements?
in octaves of 7
why was newlands work critiqued?
-some of his groups contained elements with no similar properties
-he mixed up metals and non-metals
-didn’t leave gaps for undiscovered elements
what did mendeleev do different to newlands?
left gaps