# Atomic structure - Short answer questions

Some short answer questions will be multiple choice questions. These will appear in both exam papers, and at both Tiers. Multiple choice questions are asked as questions, often starting with 'What is …' or 'Which of these …'.

You have four options to choose from in a multiple choice question. You must only choose one of these options, by writing your answer (A, B, C, or D) in a box.

It may help to reject any answers that you feel are obviously wrong, so that you can focus on choosing the right answer.

Other short answer questions will start with command words such as 'describe' or 'explain'. Some command words are easy to understand such as:

• 'calculate' or 'determine' for maths questions
• 'complete' to fill in a gap in a table or graph
• 'define' to give the meaning of an important word
• 'suggest' where you use your knowledge in an unfamiliar situation

The command words 'describe' and 'explain' can be confusing. If you are asked to describe a graph, you will be expected to write about its overall shape, whether it is linear or curved, the slope of gradients etc. If you are asked to explain why a pattern or trend is seen in a graph, you will be expected to use your science knowledge, not just say what you see (which is a description), eg 'The graph shows a steep linear increase for the first three hours because…'.

'Explain how' and 'why' questions often have the word 'because' in their answer. 'Describe' questions don't.

The number of marks per question part is given in this form '[2 marks]'. It is essential that you give two different answers if a question is worth two marks. Sometimes you can gain a second mark by giving the units in a calculation or stating specific data points, eg the speed of the object decreased by 8 m/s.

Questions courtesy of Eduqas.

## Sample question 1 - Foundation

Question

Complete the following paragraph about a nuclear reactor by underlining the correct word or words in each of the brackets. [5 marks]

The absorption of (slow protons / slow neutrons / slow electrons) can cause a (fusion / fission / chemical) reaction in uranium nuclei. The particles are slowed down by (a moderator / control rods / concrete shielding). The emission of (protons / neutrons / electrons) in this reaction can cause a chain reaction. An uncontrolled chain reaction is prevented by using (a moderator / control rods / concrete shielding).

The absorption ofslow neutronscan cause afissionreaction in uranium nuclei. The particles are slowed down bya moderator. The emission ofneutronsin this reaction can cause a chain reaction. An uncontrolled chain reaction is prevented by usingcontrol rods.

## Sample question 2 - Higher

Question

Radioactive isotopes are also used in quite a few applications. Americium-241 is a radioactive isotope which is used in smoke detectors. It decays into neptunium by giving out an alpha particle.

a) What are the missing numbers, x and y, in the decay equation below. [2 marks]

b) Explain why the radiation from a smoke detector presents no danger to people living in a house. [2 marks]

a)x = 95

y = 237

b) The alpha particles emitted are stopped by the plastic casing and also are stopped by air between the source and people.