GCSE AQA Trilogy Models of the atom - AQA Further developments to the atomic model The idea of the atom as the building block of matter has developed over time. What was thought of as a single ...

Chadwick repeated their experiments but with the goal of looking for a neutral particle -- one with the same mass as a proton, but with zero charge. His experiments were successful.

Source: Encyclopaedia Britannica In 1943, Chadwick travelled as head of the British mission to Los Alamos in the US, where scientists were developing the first atomic bomb.