6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
Scientists' picture of the atom changed many times between 1803 and 1932. Each new model was the result of new experimental evidence.
Describe how the model of the atom developed from Dalton's model through to the nuclear model established by Rutherford and Bohr, and explain how the alpha-particle scattering experiment provided the evidence that overturned the earlier "plum pudding" model. (6 marks)
Chlorine exists naturally as two isotopes. A sample of chlorine contains:
| Isotope | Mass number | Abundance (%) |
|---|---|---|
| chlorine-35 | 35 | 75.0 |
| chlorine-37 | 37 | 25.0 |
(a) State what is meant by the term isotopes. (1 mark)
(b) Both isotopes have the atomic number 17. Give the number of protons, neutrons and electrons in one atom of chlorine-37 (1737Cl). (1 mark)
(c) Calculate the relative atomic mass of chlorine in this sample. Give your answer to 1 decimal place and show your working. (2 marks)
A student heats a small block of solid stearic acid in a tube until it is well above its melting point, then lets it cool. They measure the temperature every 30 seconds and plot a cooling curve. The curve falls, then stays flat at a constant temperature for several minutes, then falls again.
(a) Using the particle model, explain why the temperature stays constant during the flat part of the cooling curve, even though the substance is still losing heat to the surroundings. (2 marks)
(b) Describe how the arrangement and movement of the particles change as the stearic acid changes from a liquid to a solid. (1 mark)
An atom of potassium has the atomic number 19 and the mass number 39.
(a) Determine the number of protons, neutrons and electrons in this atom. (1 mark)
(b) Write the electronic structure of a potassium atom (for example, in the form 2,8,...). (1 mark)
(c) State the relative charge and the relative mass of a single electron. (1 mark)
The table gives information about three subatomic particles.
| Particle | Relative charge | Relative mass | Location in the atom |
|---|---|---|---|
| proton | A | 1 | nucleus |
| neutron | 0 | B | nucleus |
| electron | −1 | very small | C |
Complete the table by giving the correct entries for A, B and C. (2 marks)
The radius of a typical atom is about 1×10−10 m. The radius of its nucleus is about 1×10−14 m.
Calculate how many times larger the radius of the atom is than the radius of its nucleus. (1 mark)