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.

Since a nucleus contains protons and neutrons, most of the mass of an atom is concentrated in its nucleus.

Atoms are very small, they have a radius of around 1 × 10-10 metres.

In 1919 Rutherford had discovered the proton, a positively charged particle within the atom's nucleus ... He called it a neutron, and imagined it as a paired proton and electron.

When a carbon-14 atom decays, one of its eight neutrons turns into a proton, emitting an electron (with a charge of -1) in the process. The atom is now stable. And with seven protons and seven ...