Question

how is an electron related to atomic mass

how is an isoptope related to mass number

I truly do not understadn how they are realted any help

Answer 1

how is an electron related to atomic mass?
Electrons are less than 1/1000 of the mass of an atom. When atomic mass is measured, it includes the small mass of the electrons.

how is an isotope related to mass number ?
I believe I answered that question already, in response to another of your posts. Different isotopes of the same element have different numbers of neutrons, but the same number of protons. The atomic mass number of an isotope is very nearly equal to the total number of protons and neutrons. There are small differences from that rule, however, due to the presence of electrons and differences in nuclear binding energy, which is the source of nuclear power.

If you don't understand the last sentence, never mind. You will probably learn about that later.