questioning vs skeptical

questioning is a noun but skeptical is not a noun.

Word	Noun	Adjective	Verb	Adverb
questioning	Yes	Yes	No	No
skeptical	No	Yes	No	No

As adjectives, questioning and skeptical are synonyms defined as:

Other synonyms of questioning include doubting, sceptical.

questioning (noun)	skeptical (noun)
a request for information

questioning (adjective)	skeptical (adjective)
showing curiosity	marked by or given to doubt
marked by or given to doubt	denying or questioning the tenets of especially a religion
perplexed (as if being expected to know something that you do not know)