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Practise 29 exam-style questions on The structure of an atom for AQA GCSE Physics. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Electrons in an atom are arranged at different distances from the nucleus.
What name is given to these different distances?
Energy levels (shells).
Each distance from the nucleus corresponds to a particular energy. The further an energy level is from the nucleus, the higher its energy.
energy levels
allow shells
The electrons in an atom stay in the atom rather than flying away.
Explain why.
The electrons are negatively charged and the nucleus is positively charged. Opposite charges attract, so the electrons are attracted to the nucleus, which keeps them in the atom.
The attraction between opposite charges holds the atom together. If an electron gains enough energy, it can escape this attraction completely, leaving a positive ion.
electrons are negative and the nucleus is positive
so there is a force of attraction between the electrons and the nucleus
allow opposite charges attract; allow electrostatic attraction
An atom has a radius of 1 × 10⁻¹⁰ m.
Calculate how many of these atoms would fit side by side in a line 1 mm long.
Each atom takes up its diameter: 2 × 1 × 10⁻¹⁰ = 2 × 10⁻¹⁰ m
1 mm = 1 × 10⁻³ m
Number of atoms = 1 × 10⁻³ ÷ (2 × 10⁻¹⁰) = 5 × 10⁶
Atoms side by side each take up a width equal to their diameter, which is twice the radius. Convert millimetres to metres before dividing. Five million atoms in a single millimetre shows how tiny atoms are.
diameter of atom = 2 × 10⁻¹⁰ m
an answer of 5 × 10⁶ scores 3 marks
1 mm = 1 × 10⁻³ m
number = 1 × 10⁻³ ÷ 2 × 10⁻¹⁰ = 5 × 10⁶
allow 5 000 000; using the radius instead of the diameter gives 1 × 10⁷ and scores 2 marks
A student's notes say:
"Electrons can orbit the nucleus at any distance. When an atom absorbs light, one of its electrons moves closer to the nucleus."
Identify the two mistakes in the student's notes and correct them.
The first mistake is that electrons can be at any distance from the nucleus. In fact electrons are only found at specific distances from the nucleus, in particular energy levels. The second mistake is that absorbing light makes an electron move closer to the nucleus. In fact absorbing electromagnetic radiation makes an electron move further from the nucleus, to a higher energy level; an electron moves closer to the nucleus when the atom emits radiation.
Electrons occupy fixed energy levels. Gaining energy (absorption) moves an electron outwards to a higher level, and losing energy (emission) moves it inwards to a lower level.
mistake 1: electrons cannot be at any distance from the nucleus
correction: electrons are only found at specific distances / in particular energy levels
mistake 2: absorbing light does not make an electron move closer to the nucleus
correction: absorbing radiation makes the electron move further from the nucleus, to a higher energy level
allow moving closer happens when radiation is emitted
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