1. 1
   A physics class recreates the historic Geiger-Marsden experiment, firing a beam of alpha particles at a very thin sheet of gold foil and recording where the particles land on a detector screen surrounding the foil.

   (a)

   In the alpha particle scattering experiment, most alpha particles fired at the thin gold foil passed straight through with little or no deflection. What does this observation suggest about the structure of the atom?

   [1 mark]

   • AMost of the atom is empty space
   • BThe atom is a solid sphere of positive charge
   • CAll the mass of the atom is spread evenly throughout it
   • DThe nucleus is larger than the atom itself

   (b)

   A very small number of alpha particles in the experiment bounced almost straight back from the foil. What does this show about the nucleus?

   [1 mark]

   • AThe nucleus is negatively charged and very light
   • BThe nucleus contains a concentration of positive charge and most of the atom's mass
   • CThe nucleus is the same size as the whole atom
   • DThe nucleus has no charge at all

   (c)

   Explain why only a very small fraction of the alpha particles were deflected by large angles, in terms of the size and position of the nucleus within the atom.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   During a lesson, a student builds a table listing the number of protons, neutrons and electrons in different particles, and then uses it to work out whether given particles are neutral atoms or ions.

   (a)

   A student is completing a table comparing the relative charges of the three subatomic particles. What is the relative charge of a neutron?

   [1 mark]

   • A+1
   • B-1
   • C0
   • D+2

   (b)

   An atom that normally has an equal number of protons and electrons loses one electron. What does the atom become?

   [1 mark]

   • AA neutron
   • BA negative ion
   • CA different element
   • DA positive ion

   (c)

   Explain, in terms of protons and electrons, why an atom that has not lost or gained any particles is electrically neutral overall.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A hospital's radiotherapy department stores two forms of the element cobalt, used for treating cancer, written using standard notation as $^{59}_{27}\text{Co}$ and $^{60}_{27}\text{Co}$.

   (a)

   A hospital radiotherapy department uses two forms of cobalt written as $^{59}_{27}\text{Co}$ and $^{60}_{27}\text{Co}$. State the number of protons, neutrons and electrons in a neutral atom of each form.

   [3 marks]

   (b)

   Explain what is meant by the term isotopes, and use it to explain why $^{59}_{27}\text{Co}$ and $^{60}_{27}\text{Co}$ have identical chemical properties but different masses.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A group of history-of-science students is studying how the atomic model changed in the early twentieth century after Rutherford's team analysed the results of firing alpha particles at thin gold foil.

   (a)

   Before the alpha scattering experiment, scientists believed atoms matched the plum pudding model. Describe this model and explain how the results of the alpha scattering experiment led scientists to replace it with the nuclear model of the atom.

   [6 marks]

   (b)

   Explain, using the observed pattern of alpha particle deflections and ideas about atomic radius, why scientists concluded that the nucleus must be small, dense and positively charged.

   [6 marks]

   Total for question 4: 12 marks

End of questions