History Of Periodic Table

Question 1

Dobereiner

Answer 1

Noticed that there were groups of three elements with similar properties and the atomic weight of these elements was midway between the other two he called these groups of three elements ‘’triads’’

Question 2

Newlands

Answer 2

Listed the elements known at the time in order of increasing atomic weight and noticed that every 8th element has similar properties to the first one.
This only worked for the first 16 elements but was an important discovery because it showed that the elements had periodic properties
Called this development “law of octaves”
Does not apply to todays periodic table as today we have noble gases and Newlands did not

Question 3

Mendeleev

Answer 3

Listed the elements in order of increasing atomic weight. Placed elements with similar properties under each other. Left gaps for undiscovered elements and predicted what these elements would be like.
Reversed the order of pairs of elements so that they would be listed in groups of similar properties

Question 4

Mosley

Answer 4

Discovered that the nucleus of each element contained a positive charge of a definite amount.
This is the atomic number of each element.