Your saying Satan was the serpent in the Garden.
But however look at this
Ezekiel
who's this speaking of
“‘You were the seal of perfection,
full of wisdom and perfect in beauty.
13 You were in Eden,
the garden of God;
every precious stone adorned you:
carnelian, chrysolite and emerald,
topaz, onyx and jasper,
lapis lazuli, turquoise and beryl.[
b]
Your settings and mountings[
c] were made of gold;
on the day you were created they were prepared.
14 You were anointed as a guardian cherub,
for so I ordained you.
You were on the holy mount of God;
you walked among the fiery stones.
15 You were blameless in your ways
from the day you were created
till wickedness was found in you.
16 Through your widespread trade
you were filled with violence,
and you sinned.
So I drove you in disgrace from the mount of God,
and I expelled you, guardian cherub
Two points of reference here
I'm pretty convinced the above passage is referring to satan.
If you could see he was described as being in the garden of eden but if you read on further he was described as perfect beauty rich in wisdom and a guardian cherub.
At the point of being in eden.
If you read on further we still see he was still thought of as the same person on the holy mount of God which is mount Sinai where the ten commandments where given
Which as you know is well after eden.
It also says he was expelled Cast out become wicked at the point of time from the mount of God which is the days of Moses.