mantel vs mantelpiece

mantel and mantelpiece both are nouns.

Word	Noun	Adjective	Verb	Adverb
mantel	Yes	No	No	No
mantelpiece	Yes	No	No	No

As nouns, mantel and mantelpiece are synonyms defined as:

Other synonyms of mantel include chimneypiece, mantle, mantlepiece.

mantel (noun)	mantelpiece (noun)
shelf that projects from wall above fireplace	shelf that projects from wall above fireplace