Homework problem 2C.3

[SarahSteffen_LEC4]

On this homework problem, we are asked to draw lewis structures for ion like the periodate ion and the hydrogen phosphate ion, but the problem doesn't provide you with any formula for these ions. So, I'm wondering whether or not we are expected to just know the formulas of these ions?

[ALegala_2I]

As of right now, I believe that we do not need to memorize the molecular formula for these molecules since we did not cover it in class. On a test, I think it would be given to us and we would just have to draw the lewis structure.

[AniP_2D]

For now, I don't think we're expected to know the formulas.

[EvanWang]

I asked my TA and he said that we aren't expected to know nomenclature right now, but I would try to memorize the important polyatomic ions like phosphate.

[Sanjana Munagala_1j]

For this same question since the elements after period 3 can have expanded octets, they can hold up to 18 electrons right? So how come for part a, we couldn't double bond all the oxygen atoms to iodine? This problem is consistent with the other parts of the problem as well.
Thanks

[Sanjana Munagala_1j]

Actually sorry, I understand why I can't do all double bonds for a and b because of wanting the formal charge on the atom with the highest electron affinity. However, for part c why can't we bond the atom h and atom cl and then double bond the rest of the oxygen atoms with cl? Wouldn't this reduce the formal charge for all the atoms to zero?
Thanks