The history of the periodic table

Question 1

Which extra group of elements was added into the modern periodic table?

Answer 1

Nobel gases

Question 2

What did Mendeleev do that was different to previous scientists when predicting the PT?

Answer 2

1) Left gaps for undiscovered elements
2) Predicted properties of the undiscovered elements

Question 3

Why couldn’t Mendeleev have ordered his PT in order of atomic number?

Answer 3

Atomic number is based on protons, and protons were not discovered yet

Question 4

Why did Mendeleev reverse the order of some pairs of elements?

Answer 4

So their properties matched the rest of the group

Question 5

Newlands PT Vs Modern PT

Answer 5

Newlands: No noble gases, Metals and non-metals not separated, arranged in increasing mass number, halogens are in first group

Question 6

How did Newlands arrange elements in his version of the PT?

Answer 6

In order of atomic weight, in rows of 7 elements (as he thought every 8th element seemed similar). He didn’t leave gaps for undiscovered elements.

Question 7

How did John Dalton arrange elements in his PT?

Answer 7

In order of atomic weight. Left no gaps. Symbols used not as we know them today.

Question 8

How is the modern periodic table arranged?

Answer 8

In order of atomic number (proton number)