Ca vs calcium

Ca and calcium both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ca	Yes	No	No	No
calcium	Yes	No	No	No

As nouns, Ca and calcium are synonyms defined as:

Ca and calcium: a white metallic element that burns with a brilliant light; the fifth most abundant element in the earth's crust; an important component of most plants and animals

Other synonyms of Ca include atomic number 20.

Ca (noun)	calcium (noun)
a white metallic element that burns with a brilliant light; the fifth most abundant element in the earth's crust; an important component of most plants and animals	a white metallic element that burns with a brilliant light; the fifth most abundant element in the earth's crust; an important component of most plants and animals