The picture shows a close-up of one carbon atom. A hydrogen atom has one proton as the nucleus and one electron in the region outside the nucleus. The electron and proton are attracted to each other.

He called it a neutron, and imagined it as a paired proton and electron. There was no evidence for any of these ideas. Chadwick kept the problem in the back of his mind while working on other things.

a proton in the lithium nucleus is resonantly excited by the interaction with the electron and promptly decays into a neutron and a positively charged pion. If this neutron subsequently transfers ...

The emission of beta radiation provides evidence that neutrons and protons are made up of quarks. Beta (\(\beta^-\)) decay is the release of an electron by the change of a neutron to a proton.

He called it a neutron, and imagined it as a paired proton and electron. There was no evidence for any of these ideas. Chadwick kept the problem in the back of his mind while working on other things.