5.1.2.2 development of the periodic table

Question 1

Before the discovery of protons, neutrons and electrons, scientists attempted to…

Answer 1

Classify the elements by arranging them in order of their atomic weights.

Question 2

The early periodic tables were incomplete and some elements were places in inappropriate groups if the strict order of ________ _______ was followed.

Answer 2

Atomic weights

Question 3

Mendeleev overcame some of the problems by..

Answer 3

Leaving gaps for elements that he thought had not been discovered and I’m some places changed the order based on atomic weights.