effectiveness vs effectual

effectiveness is a noun but effectual is not a noun.

Word	Noun	Adjective	Verb	Adverb
effectiveness	Yes	No	No	No
effectual	No	Yes	No	No

effectiveness (noun)	effectual (noun)
power to be effective; the quality of being able to bring about an effect
capacity to produce strong physiological or chemical effects

effectiveness (adjective)	effectual (adjective)
	producing or capable of producing an intended result or having a striking effect
	having legal efficacy or force