What is a neutron?

Free neutrons decay by emission of an electron and an electron antineutrino to become a proton after 14,8 minutes. (Graphics: FRM II/TUM)

Neutrons, together with protons, make up atomic nuclei. With the exception of the hydrogen atom (H), whose core consists of only one proton, the nuclei of all elements consist of protons and neutrons. The number of neutrons is usually at least equal, but most of the time significantly greater, than the number of protons.

 

 

 

 

Some fundamental properties of the neutron.

Mass

1,674 × 10-27 kg

Charge

outwardly neutral

Diameter

1,7 × 10-15 m

Lifetime (as free particle, stable in the atomic nucleus)

880,1 s

Substructure

1 up and 2 down quarks