How can you say that electron is a universal constituent of all atoms ?

Explanation

The discharge tube experiments proved that electron is a universal constituent of all the atoms. The electrons constituting the cathode rays are all identical irrespective of the material of cathode or gas used in the discharge tube. All the electrons have same
m
e
​
ratio, where e is the charge of an electron (1.×10
−19
coulombs), and m is the mass of an electron (9.1×10
−31
...