1. 1
   A school textbook describes how, in 1869, Dmitri Mendeleev arranged the known elements into a table in order of increasing atomic weight, but left gaps in the table for elements he believed had not yet been discovered, and even predicted their properties.

   (a)

   A school textbook is describing how, in 1869, Dmitri Mendeleev arranged the known elements into a table in order of increasing atomic weight, but left gaps for elements he believed had not yet been discovered.
   
   Why was leaving these gaps an important part of Mendeleev's work?

   [1 mark]

   • AIt allowed elements with similar properties to remain grouped together in the same column
   • BIt made the table look neater on the page
   • CIt reduced the total number of elements needed
   • DIt removed the need to know atomic weights

   (b)

   Mendeleev also swapped the order of a few elements, placing them out of strict order of atomic weight, so that they fitted better with elements sharing similar properties.
   
   What does this decision show about how Mendeleev built his periodic table?

   [1 mark]

   • AHe ignored atomic weight completely
   • BHe prioritised grouping elements with similar chemical properties together, even over strict atomic weight order
   • CHe arranged elements alphabetically by name
   • DHe arranged elements randomly based on when they were discovered

   (c)

   Explain how the later discovery of isotopes helped to explain why ordering elements strictly by atomic weight sometimes placed them in an incorrect position in the periodic table.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A materials scientist is choosing a metal to build electrical contacts for a switch and is comparing its properties with a sample of sulfur, a non-metal, using their positions in the modern periodic table.

   (a)

   Which statement correctly describes a key difference between metals and non-metals, as shown by their positions in the periodic table?

   [1 mark]

   • AMetals are found on the right-hand side of the periodic table and form negative ions
   • BThere is no link between an element's position in the periodic table and whether it is a metal or non-metal
   • CNon-metals form positive ions more readily than metals
   • DMetals are found on the left and towards the bottom of the periodic table and form positive ions

   (b)

   The materials scientist notes that the metal she has chosen conducts electricity well, while sulfur does not. Which statement best explains this difference in terms of atomic structure and bonding?

   [1 mark]

   • AMetals have more protons than non-metals in every case
   • BSulfur atoms are much larger than metal atoms
   • CMetal atoms have delocalised electrons that are free to move through the structure and carry charge, while sulfur has no such free electrons
   • DNon-metals always have a higher melting point than metals

   (c)

   Explain how the atomic structure of a typical metal relates to its position on the left-hand side of the periodic table, and how this differs from a typical non-metal on the right-hand side.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An environmental chemist is studying the noble gases in Group 0 because they are used to fill protective display cases at a historical document archive, preventing the documents inside from reacting with oxygen in the air.

   (a)

   An environmental chemist is studying the noble gases, found in Group 0 of the periodic table, because they are used to fill the protective atmosphere inside historical document display cases in an archive, preventing the documents from reacting with oxygen. Describe why the noble gases are so unreactive, and describe the trend in their boiling points down the group.

   [3 marks]

   (b)

   The archive is deciding between using helium or argon to fill the display cases. Using the position of these two elements in Group 0 and the general trends of the group, predict and explain which of the two elements would have the higher boiling point, and explain why both gases would be equally suitable in terms of reactivity.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A chemical safety officer is training new warehouse staff on why certain elements must be stored and handled very differently, even though they may appear in the same general area of the periodic table, focusing on how position relates to atomic structure and reactivity.

   (a)

   Using the position of elements in the periodic table, explain how the arrangement of the periodic table into groups and periods allows chemists to predict an element's properties and likely reactions, using specific reference to how atomic structure changes across a period and down a group.

   [6 marks]

   (b)

   One new member of staff suggests that all metals must be equally reactive, since they are all found on the left-hand side of the periodic table. Evaluate this claim, using the properties of transition metals compared with Group 1 metals as evidence, and explain how atomic structure accounts for the differences.

   [6 marks]

   Total for question 4: 12 marks

End of questions