Fundamental Particles of the Atom

From Lecture 1 on 1/14/25

proton mass

1 amu (large)

proton charge

+1 electron volt (eV)

proton defines the

element

protons were isolated by

Goldstein in 1886 canal (cathode) ray experiment

electron mass

1/1000 amu (neglible)

electron charge

-1 electron volt (eV)

electron location

in orbit outside the nucleus

electron defines the

ion (charge) and size

electrons were isolated by

Thomson in 1897 in canal rays experiment (measured charge to mass ratio)

Millikan in 1909 oil drop experiment (calculated charge of a single one)

neutron mass

1 amu (large)

neutron charge

0

neutron location

nucleus

neutron defines the

isotope (mass)

neutrons were isolated by

Chadwick in 1932 in α-particle scattering experiment