1.11 Mendeleev and the development of the periodic table
5 exam questions worth 11 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
0 / 11
Why did Mendeleev leave gaps in his periodic table?
Choose one answer.
Correct Not quite: the answer is For elements that had not yet been discovered
Mark scheme
C
Model answer
C: he left gaps for elements he believed existed but had not yet been discovered.
Describe how Mendeleev arranged the elements in his periodic table.
Mark scheme
- in order of atomic weight (1)
- put elements with similar properties in the same group / swapped some to fit properties (1)
Model answer
He put the elements in order of atomic weight, but placed elements with similar properties together in groups, even if that meant changing the order.
Explain why other scientists came to accept Mendeleev's periodic table.
Mark scheme
- he left gaps for undiscovered elements (1)
- he predicted the properties of these elements (1)
- elements such as germanium/gallium were later discovered with properties that matched his predictions (1)
Model answer
Mendeleev left gaps for elements not yet discovered and predicted their properties. When elements such as germanium and gallium were found, they fitted the gaps and had properties very close to his predictions.
Tellurium has a relative atomic mass of 128. Iodine has a relative atomic mass of 127. In the periodic table, iodine comes after tellurium.
Explain why.
Mark scheme
- iodine has similar properties to chlorine and bromine so belongs in Group 7 (1)
- elements are ordered by atomic number; iodine (53) has one more proton than tellurium (52) (1)
- tellurium has a greater proportion of heavier isotopes / more neutrons, so a higher relative atomic mass (1)
Model answer
Iodine has properties like chlorine and bromine, so it belongs in Group 7. The modern table is in order of atomic number: iodine has 53 protons and tellurium 52. Tellurium's relative atomic mass is higher because it has more of its heavier isotopes.
Mendeleev's table did not contain Group 0. Suggest why.
Mark scheme
- the noble gases had not been discovered (1)
- they are unreactive, so they do not form compounds / were hard to detect (1)
Model answer
The noble gases had not been discovered yet, because they are so unreactive that they are not found in compounds and were hard to detect.
Found a mistake?