Ac vs atomic number 89

Ac and atomic number 89 both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ac	Yes	No	No	No
atomic number 89	Yes	No	No	No

As nouns, Ac and atomic number 89 are synonyms defined as:

Ac and atomic number 89: a radioactive element of the actinide series; found in uranium ores

Other synonyms of Ac include actinium.

Ac (noun)	atomic number 89 (noun)
a radioactive element of the actinide series; found in uranium ores	a radioactive element of the actinide series; found in uranium ores