topic 1b - the periodic table (1. development of the periodic table)

Question 1

how is the periodic table organised today

Answer 1

by atomic number (protons)

Question 2

how was the periodic table organised before the 20th century

Answer 2

by atomic weight, so elements ended up with other elements which didn’t have the same properties.

Question 3

how did mendeleev organise the periodic table

Answer 3

organised the known elements in order of atomic weight but switched the order of some elements if they had similar properties. gaps were left to make sure that elements with similar properties stayed in the same group.

Question 4

give one piece of evidence that strongly suggested Mendeleev’s system of ordering was correct?

Answer 4

new elements were found which fit into Mendeleev’s table