1932Reputable sourceWell documented
Chadwick Discovers the Neutron
On the timeline · around 1932 ·
What happened
In 1932 the British physicist James Chadwick discovered the neutron — a particle in the atomic nucleus with almost the same mass as a proton but no electric charge. It completed the basic picture of the atom: a nucleus of protons and neutrons surrounded by electrons.
Why it matters
The neutron explained the makeup of atomic nuclei and, because it is uncharged, proved the perfect tool for probing and splitting them — making possible the nuclear fission discovered just six years later. Chadwick won the 1935 Nobel Prize.
Sources
- The Nobel Prize. James Chadwick – Facts (Nobel Prize in Physics 1935) · Reputable source