seventh heaven vs walking on air

seventh heaven and walking on air both are nouns.

Word	Noun	Adjective	Verb	Adverb
seventh heaven	Yes	No	No	No
walking on air	Yes	No	No	No

As nouns, seventh heaven and walking on air are synonyms defined as:

Other synonyms of seventh heaven include bliss, blissfulness, cloud nine.

seventh heaven (noun)	walking on air (noun)
a state of extreme happiness	a state of extreme happiness