1. Who was the first scientist to propose that atoms of different elements have different masses?

a) John Dalton
b) John Newlands
c) Dmitri Mendeleev
d) Johann Wolfgang Döbereiner

2. What was Döbereiner's main contribution to the development of a periodic table?

a) He left gaps for undiscovered elements
b) He identified triads of elements with similar chemical properties
c) He suggested arranging elements by their atomic number
d) He arranged the elements strictly by their atomic mass

3. What was the main idea behind John Newland's Law of Octaves?

a) Elements should be arranged in groups of three
b) Every eighth element had similar chemical properties
c) Elements should be arranged by their atomic number
d) Elements with similar properties should be placed randomly

4. Newlands and Mendeleev arranged the elements in their periodic table according to their atomic ; however in the modern periodc table the elements are arranged according to their number.

5. What was Mendeleev's key improvement to the development of a periodic table?

a) He left gaps for undiscovered elements and predicted their properties.
b) He arranged the elements according to their atomic number
c) He used the Law of Octaves
d) He grouped the metals and non-metals together

6. What was the main issue with arranging elements strictly by atomic mass?

a) The masses of some elements had been incorrectly measured
b) Some elements did not always fit into groups with similar chemical properties when arranged by their atomic mass
c) Atomic mass changes over time
d) It did not leave room for newly discovered elements

7. What key discovery resolved Mendeleev's tellurium-iodine issue?

a) The existence of isotopes
b) The discovery of the proton
c) The rearrangements of the periodic table to put the transition metals in a separate block
d) The use of atomic number instead of atomic mass to arrange the elements

8. Why was Mendeleev's periodic table widely accepted?

a) He grouped the elements strictly by their atomic masses
b) He discovered new elements himself
c) He predicted the properties of undiscovered elements which were later confirmed correct
d) He discovered isotopes

9. What was main mistake Newland's make in constructing his periodic table?

a) He grouped elements only by their physical properties
b) He left gaps for undiscovered elements
c) He assumed all the elements had been discovered
d) He used incorrect atomic masses

10. Why did Mendeleev leave gaps in his periodic table?

a) He misplaced some elements
b) He followed the Law of Octaves
c) He avoided the heavy metal elements
d) He predicted more elements were yet to be discovered

11. What allowed scientists to finally arrange the elements correctly in the periodic table?

a) The discovery of atomic numbers
b) The discovery of electron shells
c) The discovery of isotopes
d) The discovery of the Octet rule