In 1932, James Chadwick discovered a new particle in the nucleus of the atom. Before this discovery, scientists could not explain why a helium atom has about four times the mass of a hydrogen atom but only two protons.
Name the particle that Chadwick discovered.
Explain how Chadwick's discovery explained the mass of a helium atom. A hydrogen atom has one proton.
Compare the plum pudding model of the atom with the modern model of the atom.
46 exam-style questions on Edexcel GCSE Chemistry 2.1 Atomic structure, covering 2.1.1 Development of the atomic model, 2.1.2 Structure of the atom and subatomic particles, 2.1.3 Mass number, isotopes and relative atomic mass, and 2.1.4 Calculating relative atomic mass from isotopic abundance. Each one has a worked solution and a mark scheme showing where the marks go.