unstable vs unstableness

unstable is not a noun while unstableness is a noun.

Word	Noun	Adjective	Verb	Adverb
unstable	No	Yes	No	No
unstableness	Yes	No	No	No

unstable (noun)	unstableness (noun)
	the quality or attribute of being unstable and irresolute

unstable (adjective)	unstableness (adjective)
lacking stability or fixity or firmness
subject to change; variable
suffering from severe mental illness
disposed to psychological variability
highly or violently reactive
affording no ease or reassurance