1. 1
   A student is shown a simple model of a sodium atom: a small central nucleus containing protons and neutrons, surrounded by electrons arranged in shells around the nucleus.

   (a)

   In a simple model of a sodium atom, the nucleus contains protons and neutrons, surrounded by electrons. What is the relative electrical charge of a proton?

   [1 mark]

   • A+1
   • B0
   • C−1
   • D+2

   (b)

   What is the relative electrical charge of an electron?

   [1 mark]

   • A+1
   • B−1
   • C0
   • D−2

   (c)

   Explain why the sodium atom shown in the model has no overall electrical charge.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An atom of aluminium has an atomic number of 13 and a mass number of 27.

   (a)

   What does the atomic number of an atom represent?

   [1 mark]

   • AThe number of electron shells in the atom
   • BThe number of neutrons in the atom
   • CThe total number of protons and neutrons
   • DThe number of protons in the atom

   (b)

   What does the mass number of an atom represent?

   [1 mark]

   • AThe number of electrons only
   • BThe number of protons only
   • CThe sum of the number of protons and neutrons
   • DThe number of neutrons only

   (c)

   Calculate the number of protons, neutrons and electrons in this atom of aluminium, showing how you worked out each value.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An unknown atom, X, has 17 protons and a mass number of 35.

   (a)

   State the number of protons, neutrons and electrons in this atom.

   [3 marks]

   (b)

   Explain, using the definitions of atomic number and mass number, how you determined each of the values in part (a), and explain why the number of electrons must equal the number of protons in this atom.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A student compares two atoms: an atom of chlorine, which has 17 protons and 18 neutrons, and an atom of potassium, which has 19 protons and 20 neutrons.

   (a)

   Describe the structure of an atom, including the location, relative charge and relative mass of each type of sub-atomic particle, and explain the significance of the fact that atoms have no overall electrical charge.

   [6 marks]

   (b)

   Using the information given, compare the numbers of protons, neutrons and electrons in the chlorine atom and the potassium atom, explaining how you determined each value and why each atom has no overall charge.

   [6 marks]

   Total for question 4: 12 marks

End of questions