1. 1
   A school science museum displays a model of an atom of sodium (proton number 11, nucleon number 23) showing a central nucleus surrounded by shells of electrons.

   (a)

   Which of the following correctly states the particles found in the nucleus of the atom?

   [1 mark]

   • AProtons and neutrons
   • BProtons and electrons
   • CNeutrons and electrons only
   • DElectrons only

   (b)

   The sodium atom has a proton number of 11 and a nucleon number of 23. Which electronic configuration correctly represents the arrangement of electrons in shells for this sodium atom?

   [1 mark]

   • A2,8,2
   • B2,8,1
   • C2,9
   • D8,2,1

   (c)

   Using the proton number (11) and nucleon number (23) of this sodium atom, calculate the number of protons, neutrons and electrons it contains.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A chemistry teacher shows students the Periodic Table and points out that argon (proton number 18), in Group VIII, has the electronic configuration 2,8,8, while chlorine (proton number 17), in Group VII, has the electronic configuration 2,8,7.

   (a)

   Which statement correctly explains why argon does not readily react with other elements?

   [1 mark]

   • AArgon has no electrons in its outer shell
   • BArgon has only one electron in its outer shell
   • CArgon has a full outer shell of electrons
   • DArgon's nucleus contains no neutrons

   (b)

   The teacher also points out that chlorine, in Group VII, has the electronic configuration 2,8,7. Based on the relationship between group number and the number of electrons in the outer shell, how many electrons would an atom of an element in Group V of the Periodic Table have in its outer shell?

   [1 mark]

   • A8
   • B3
   • C7
   • D5

   (c)

   State the relationship between the period number of an element and its electronic configuration, and use this relationship to explain how many electron shells an atom of an element in Period 3 would have.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A physicist studies the atomic model and compares the relative charges and relative masses of the three subatomic particles, using an atom of aluminium (proton number 13, nucleon number 27) as an example.

   (a)

   State the relative charge and relative mass of a proton, a neutron and an electron.

   [3 marks]

   (b)

   The physicist uses an atom of aluminium (proton number 13, nucleon number 27) as an example. Determine the number of protons, neutrons and electrons in a neutral aluminium atom, and use this to work out the electronic configuration of aluminium, explaining how you arrive at your answer.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A mass spectrometry laboratory analyses a sample of naturally occurring chlorine and finds it consists of two isotopes: chlorine-35, which makes up 75% of the sample, and chlorine-37, which makes up 25% of the sample.

   (a)

   Explain what is meant by the term isotopes, describe why isotopes of the same element have identical chemical properties, and calculate the relative atomic mass of this sample of chlorine, showing your working.

   [6 marks]

   (b)

   The laboratory also analyses an ion formed from one of these chlorine isotopes, represented by the symbol $^{35}_{17}$Cl$^-$. Interpret this symbol fully, stating the numbers of protons, neutrons and electrons present, and explain why this species carries an overall negative charge despite chlorine atoms themselves being electrically neutral.

   [6 marks]

   Total for question 4: 12 marks

End of questions