wakeful vs wakefulness

wakeful is not a noun while wakefulness is a noun.

Word	Noun	Adjective	Verb	Adverb
wakeful	No	Yes	No	No
wakefulness	Yes	No	No	No

wakeful (noun)	wakefulness (noun)
	a periodic state during which you are conscious and aware of the world
	the process of paying close and continuous attention
	a temporary state in which you are unable (or unwilling) to sleep

wakeful (adjective)	wakefulness (adjective)
carefully observant or attentive; on the lookout for possible danger
marked by full consciousness or alertness
(of sleep) easily disturbed