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Home · IGCSE 0625 · Nuclear physics · Atomic structure · Practice
Core · Practice questions · Atomic structure

Nucleus and electrons.

Six original Cambridge-style questions on the structure of the atom: the parts and their charges, where the mass is, why the atom is mostly empty space, and what holds the electrons in orbit.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
What the examiner wants

Clear facts, correct charges.

01
Recall
[3 marks]

Describe the structure of an atom. State what is at the centre and what is found around it.

  • There is a small nucleus at the centre. ✓
  • The nucleus is positively charged. ✓
  • Negatively charged electrons move around the nucleus in orbits. ✓
02
Recall
[2 marks]

State the charge on the nucleus and the charge on an electron.

  • The nucleus is positively charged. ✓
  • An electron is negatively charged. ✓
03
Analysis
[2 marks]

Almost all of the mass of an atom is found in one place. State where, and name the much lighter particles found in the rest of the atom.

  • Almost all the mass is in the nucleus. ✓
  • The much lighter particles are the electrons. ✓
04
Application
[2 marks]

A student says that an atom is solid all the way through. Explain why this is wrong.

  • The nucleus is extremely small compared with the whole atom. ✓
  • The electrons orbit far out, so most of the atom is empty space. ✓
05
Analysis
[2 marks]

Explain what keeps the negative electrons moving around the nucleus instead of flying away.

  • There is an electrostatic attraction between the negative electrons and the positive nucleus. ✓
  • This pull holds the electrons in their orbits. ✓
06
Application
[2 marks]

A complete atom has no overall charge. Explain why, in terms of the positive and negative charges it contains.

  • An atom has equal numbers of positive charges (in the nucleus) and negative electrons. ✓
  • The equal positive and negative charges cancel, so the atom is neutral overall. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.