Practise 25 exam-style questions on Development of the periodic table for AQA GCSE Chemistry. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
25 questions
1–6 marks each
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20 questions, marked as you go
Sample questions with model answers
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Question 1
2 marks
Early scientists could not arrange the elements in order of atomic number.
Explain why.
Model answer
Protons, neutrons and electrons had not yet been discovered, so scientists did not know that atoms contain protons or how many protons each element has. The atomic number of each element was therefore unknown.
Explanation
The atomic number is the number of protons, so it could only be used to order the elements after the proton had been discovered in the early 1900s. Before that, atomic weight was the only measurable property available.
Mark scheme
1 mark
protons (and neutrons and electrons) had not been discovered
1 mark
so the atomic number / number of protons in each atom was not known
Question 2
2 marks
Suggest two reasons why Mendeleev's periodic table was more useful than earlier tables.
Model answer
Mendeleev's table could be used to predict the properties of elements that had not yet been discovered. It also kept elements with similar properties together in the same groups, so it could be used to predict how known elements would react.
Explanation
A useful classification groups similar things together and allows predictions. Mendeleev's gaps and changes of order made both possible.
Mark scheme
1 mark
it could be used to predict the properties of undiscovered elements
max 2
1 mark
elements with similar properties were always in the same group
1 mark
it left room for new elements to be added when discovered
Question 3
3 marks
When Mendeleev first published his periodic table, some scientists did not accept it.
Suggest why.
Model answer
Mendeleev left gaps for elements that no one had discovered, and at first there was no evidence that these elements existed. He also did not always follow the order of atomic weights, which seemed to go against the measured data. Scientists only became convinced when elements were discovered that filled the gaps with the properties he had predicted.
Explanation
New scientific ideas are often treated with caution until there is evidence for them. Mendeleev's table was accepted once its predictions were confirmed.
Mark scheme
1 mark
he left gaps for elements that no one had discovered
max 3
1 mark
there was no evidence at first that these missing elements existed
1 mark
he did not always follow the order of atomic weights / he swapped some elements
1 mark
it was a new idea that challenged the tables other scientists were using
Question 4
4 marks
Compare Mendeleev's periodic table with the modern periodic table.
Model answer
Both tables put elements with similar properties into the same groups. However, Mendeleev ordered the elements by atomic weight, while the modern table orders them by atomic number. Mendeleev's table had gaps for undiscovered elements, but the modern table has no gaps and contains many more elements. Mendeleev's table also had no group for the noble gases, which the modern table includes as group 0.
Explanation
Each comparison should say how the two tables differ (or are the same) for the same feature. Ordering by atomic number is the key difference, because it removes the need to swap elements.
Mark scheme
1 mark
Mendeleev ordered elements by atomic weight, but the modern table uses atomic number
max 4
1 mark
Mendeleev's table had gaps, but the modern table has no gaps
1 mark
Mendeleev's table had no noble gases / group 0, but the modern table does
1 mark
the modern table contains more elements
1 mark
similarity: both arrange elements with similar properties in groups / columns
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