Correct
Correct
Nope.
Na2Cr2O7 is sodium dichromate (VI). The ion is
Do not worry, you may not have come accross this very often. There are quite a few like this one.

is the manganate ion.

is the chromate (VI) ion.
Just like sulfate, nitrate. Nitrite is

sulfite is

.
But sulfide is

and nitride is
