Is lobster a mollusk

Answer 1

Lobsters, are in fact, arthropods. Arthropods must have segmented body pieces and have an exoskeleton. While it may be true that that lobsters have shells, it does not have the mantle cavity that confirms that it is a mollusk.

Answer 2

No. A lobster is a crustacean. But the two invertebrate classes do have some externally similar organisms. For example, a snail is a mollusk with a hard exoskeleton.