In 1897, J.J. Thomson discovered that atoms contain tiny, negatively charged particles called electrons.
Before 1897, scientists used Dalton's model of the atom.
Explain why the discovery of electrons meant that Dalton's model had to be changed.
Thomson knew that atoms have no overall charge.
Explain how this led him to suggest the "plum pudding" model of the atom.
Bohr later changed Rutherford's nuclear model of the atom.
Describe the change that Bohr made.
The mass of a helium atom is about four times the mass of a hydrogen atom. A hydrogen nucleus contains one proton. A helium nucleus contains only two protons.
Explain how Chadwick's discovery of the neutron in 1932 explained this.
Suggest why the neutron was discovered much later than the electron and the proton.
51 exam-style questions on OCR GCSE Chemistry 1.2 Atomic structure, covering 1.2.1 Development of the atomic model, 1.2.2 The nuclear model and the size of atoms, and 1.2.3 Subatomic particles in atoms and ions. Each one has a worked solution and a mark scheme showing where the marks go.