4.1 Experimental facts
- Each nucleus has a
(positive) charge
, and integer number times the elementary charge
. This follows from the fact that atoms are
neutral!
- Nuclei of identical
charge come in different masses, all approximate
multiples of the “nucleon mass”. (Nucleon is the
generic term for a neutron or proton, which have almost the
same mass,
,
.) Masses can easily be determined by analysing nuclei
in a
mass spectrograph which can be
used to determine the relation between the charge
(the number of protons, we believe) vs. the mass.
Nuclei of identical charge (chemical type)
but different mass are called isotopes. Nuclei of
approximately the same mass, but different chemical type,
are called isobars.
4.1.1 mass spectrograph
A mass spectrograph is a combination of a
bending magnet, and an electrostatic device (to be
completed).