Is the RDF model an entity-relationship mode? Yes and no. It is great as a basis for ER-modelling, but because RDF is used for other things as well, RDF is more general. RDF is a model of entities (nodes) and relationships.
A. Ahmeti, D. Calvanese, and A. Polleres. Proceedings of the 13th International Semantic Web Conference (ISWC), volume 8796 of Lecture Notes in Computer Science, page 441-456. Springer, (2014)