No, it isn't.
Although lobsters belong to a different subphylum than Arachnida. Lobsters are 10-legged (including the claws) Crustaceans, unlike the 8-legged Spiders, ticks, and mites that are Arachnids.
Crustaceans and Arachnids (and another subphylum, Insecta) each belong to the phylum Arthropoda, meaning 'jointed foot'. If you look at the Wikipedia article on any of these, these classification 'trees' are shown in the right margin.
Arthropods
Yes, the lobster is an arthropod. In fact, the American lobster is currently the heaviest living arthropod (not counting extinct arthropods).
The honeybee, the lobster, the woodlouse, and the horseshoe crab would be four examples of arthropods.
All arthropods evolved in water.
Arthropods are invertebrate animals such as crustaceans. An arthropod that is useful to humans is the lobster, as it can be eaten.
food << lobster is an arthropod
Only some arthropods have a cephalothorax, like for example the lobster. Other arthropods have functionally separate (or non-fused) head and thorax, like many insects.
Yes, any insect with an exoskeleton is a arthropod
Lobsters are a type of crustacean. Crustaceans belong to the class of Arthropods.
Lobsters are arthropods. Only mammals (and not all of those) have nipples.
Yes, lobsters are arthropods. They belong to the phylum Arthropoda, which includes insects, spiders, crabs, and shrimp. Lobsters have hard exoskeletons, jointed legs, and segmented bodies characteristic of arthropods.
It is Insecta.The largest group of arthropods are aquatic, so things like shrimp, lobster, (and the most popular) Crab.Crab is the largest group in the arthropods.