1. 1
   In 1869 Dmitri Mendeleev published a periodic table in which the elements were arranged largely in order of increasing relative atomic mass, but he left gaps for elements he believed had not yet been discovered. He used the properties of known elements and their compounds to predict the properties of the missing elements. Later scientists discovered isotopes, which explained why a strict ordering by atomic mass sometimes placed elements in the wrong order.

   (a)

   Which statement best describes how Mendeleev used his table?

   [1 mark]

   • AHe used it to predict the existence and properties of elements not yet discovered
   • BHe used it to calculate the number of neutrons in every atom
   • CHe used it to prove that atoms could not be divided into smaller particles
   • DHe used it to show that all elements have the same melting point

   (b)

   Why did strict ordering by relative atomic mass sometimes place elements in the wrong position in Mendeleev's table, according to later scientific understanding?

   [1 mark]

   • ABecause Mendeleev did not know the charge of the electron
   • BBecause the relative abundance of isotopes of some elements affected their relative atomic mass
   • CBecause some elements have more electrons than protons
   • DBecause atomic mass depends only on the number of electrons in an atom

   (c)

   Explain how the modern periodic table resolves the ordering problem that Mendeleev encountered, by describing the property elements are now arranged by.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student is given a section of the modern periodic table showing seven horizontal periods and eighteen vertical groups. She is told that magnesium has atomic number 12 and is placed in period 3, group 2. She is asked to use this information, together with the position of other elements, to answer questions about electronic configuration and classification as metal or non-metal.

   (a)

   Which statement correctly describes how elements are arranged in the periods and groups of the periodic table?

   [1 mark]

   • AElements are arranged randomly in periods, and groups contain elements with consecutive atomic numbers
   • BElements are arranged in order of decreasing atomic number in periods, and elements with similar properties are placed in the same period
   • CElements are arranged in order of increasing atomic number in periods, and elements with similar properties are placed in the same group
   • DElements are arranged in order of increasing melting point in periods, and groups contain elements of the same colour

   (b)

   Using the position of magnesium (atomic number 12, period 3, group 2), which electronic configuration correctly represents a magnesium atom?

   [1 mark]

   • A8.2.2
   • B2.8.8
   • C2.6.4
   • D2.8.2

   (c)

   Explain how magnesium's electronic configuration relates to its position in group 2 of the periodic table, and use this reasoning to explain why magnesium is classified as a metal.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A teacher lists three elements from the periodic table: sulfur (atomic number 16), chlorine (atomic number 17) and argon (atomic number 18), all in period 3. The teacher asks the class to compare their atomic structures and to classify each element as a metal or non-metal based on its position in the periodic table.

   (a)

   State the number of protons, neutrons and electrons in a neutral atom of chlorine, given that chlorine has a mass number of 35, and explain why the number of protons in an atom of chlorine is described as unique to that element.

   [3 marks]

   (b)

   Explain, in terms of atomic structure and position in the periodic table, why sulfur and chlorine are classified as non-metals whereas an element such as sodium (atomic number 11, period 3, group 1) is classified as a metal.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A historian of science is writing about the development of the periodic table. She notes that Mendeleev arranged known elements largely by increasing relative atomic mass, grouped elements with similar properties together, and left gaps that he predicted would later be filled by undiscovered elements. She then compares this historical approach with the modern periodic table, which is arranged by atomic number and divides elements into metals and non-metals according to their electronic configurations.

   (a)

   Describe how Mendeleev constructed his periodic table and explain how he used it to predict the existence and properties of elements that had not yet been discovered.

   [6 marks]

   (b)

   Explain how the modern periodic table differs from Mendeleev's original table in the property used to order elements, and explain, using electronic configuration, how the position of an element in the modern periodic table allows the division of elements into metals and non-metals.

   [6 marks]

   Total for question 4: 12 marks

End of questions