mention vs touch on

mention is a noun but touch on is not a noun.

Word	Noun	Adjective	Verb	Adverb
mention	Yes	No	Yes	No
touch on	No	No	Yes	No

As verbs, touch on is a hyponym of mention; that is, touch on is a word with a more specific, narrower meaning than mention:

mention (noun)	touch on (noun)
an official recognition of merit
a remark that calls attention to something or someone
a short note recognizing a source of information or of a quoted passage

mention (verb)	touch on (verb)
make mention of	restore by replacing a part or putting together what is torn or broken
commend	have an effect upon
make reference to	refer to or discuss briefly
	be relevant to