Hello Ruby,
As Marie mentioned "excessive" is an adjective, it is not a noun.
"Excess" is the noun and could be an adjective as well.
The noun for "excessive" is " excessiveness ".
Both " excess" and "excessive" have basically the same meaning, yet they could be different components of the sentence ( when excess is a noun not an adjective).
They both mean beyond the normal limits, more than normal or necessary, inordinate, an overindulgence,immoderately.
Excess ( as a noun)
an excess of luggage .
Here it means the number of luggage is beyond the permitted limits.
an excess of tolerance.
Here the degree of tolerance is beyond the normal amount.
Excess ( as an adjective):
Trying to lose excess weight
The weight is more than the normal limits.
( Here "excessive" could be used as well).
Excessive:
It is only an adjective.
They asked for excessive charges.