Recall that in each atom its electrons orbit the nucleus at different set…

The idea

This statement asks you to recall a simple model of the atom used in this course. At the centre sits the nucleus, which contains protons and neutrons and carries the positive charge. Around it, electrons occupy orbits, and these orbits lie at different set distances from the nucleus rather than all at one distance. A useful picture is a set of concentric shells: an inner orbit close to the nucleus and outer orbits further away. Each electron belongs to one of these orbits, so the atom has structure rather than a random cloud of particles. When you answer a multiple-choice question, check that the option keeps both ideas: electrons orbit the nucleus, and the orbits are at different distances. Options that place electrons inside the nucleus, or that put every electron at the same distance, contradict the statement.

What earns the marks

• States that electrons orbit the nucleus.
• States that the orbits are at different set distances from the nucleus.
• Identifies the nucleus as the centre about which the electrons orbit.
• Rejects an option that places all electrons at the same distance from the nucleus.

Common mistakes and how to put them right

• Places electrons inside the nucleus.

  Put it right: Keep electrons in orbits around the nucleus.

• Assumes all electrons orbit at one single distance.

  Put it right: Recognise that the orbits are at different set distances.

• Confuses the nucleus with an orbit.

  Put it right: Treat the nucleus as the centre and the orbits as surrounding paths.

Exam tips

• Read every option and eliminate any that put electrons in the nucleus before choosing.
• Look for the option that mentions both orbiting and different distances, since the statement needs both ideas.
• Sketch concentric circles quickly if the wording is unclear, then match your sketch to the options.