The Olympians are named Zeus, Hera, Poseidon, Dionysus, Apollo, Artemis, Hermes, Athena, Ares, Aphrodite, Hephaestus, and Demeter. There Roman equivalents are Jupiter, Juno, Neptune, Bacchus, Apollo (as the Romans did not have a sun god), Diana, Mercury, Minerva, Mars, Venus, Vulcan, and Ceres.
Poseidon is one of the Twelve Olympians.
Hephaestus was one of the twelve great Olympian gods and goddess of ancinet Greek myth.
She was one of the twelve Greek Olympian gods and goddesses, and the only Olympian to be associated with the wilds and the hunt.
Hermes is one of the twelve Olympian gods, yes.
Yes, He is considered to be one of the Olympian twelve.
Yes, she is one of the twelve main ones.
Though key to training heroes at Camp Half-Blood, Chiron isn't an Olympian (defined as one of the twelve gods on thrones on Mount Olympus)
No, he isn't. He's the son of Apollo and some other person which I forgot. There are twelve Olympians
Apollo is one of twelve Olympian gods.
Because she is the goddess of the sea, wife of Poseidon on of twelve Olympian gods of the Greeks.
Athena was not a mortal hero. Athena was a Greek goddess one of the Olympian twelve.
On Olympus. Ganymede wasn't "an Olympian", either, but he was the cupbearer for the gods on Mt. Olympus. The term "the Twelve Olympians" is used to designate twelve of the most important gods and goddesses, but they weren't the only dwellers on Olympus. (Also, Hestia is included in some lists of the Twelve Olympians, as befitting her status as Zeus' elder sister.)