You're right. Electron is a countable noun, and once it's pluralised to electrons it needs many.
Mass/uncountable nouns are always singular: as much furniture as possible; or charge or space or current or gravy.
The only countable noun I can think of which might take much is "mushy peas". But again, mushy peas come as an amorphous blob of green stuff. It's literally a mass noun.
It would be as many electrons.
If google shows as much electrons, it would be the most popular form.
Just because it is the most popular form, doesn't mean it's correct.
Scince an atom's number of electrons is countable, many is needed.
If it was as much as you can fit somewhere, it wouldn't be countable so you would say as much.
I hope this was of use to you.