I was given $\ce{K2CrO4}$ and was asked to name the compound.
Can this be done by:
1) Determining the molecular compounds oxidation state
or
2) Does one need to memorize the polyatomic ions and that is the only way to know what is what?
Chemistry Stack Exchange is a question and answer site for scientists, academics, teachers, and students in the field of chemistry. It only takes a minute to sign up.
Sign up to join this communityI was given $\ce{K2CrO4}$ and was asked to name the compound.
Can this be done by:
1) Determining the molecular compounds oxidation state
or
2) Does one need to memorize the polyatomic ions and that is the only way to know what is what?
Definitely you need to remember it. Potassium Chromate is IUPAC name of $\ce{K2CrO4}$. There are other names such as Chromic acid and dipotassium salts. But mostly IUPAC names are accepted.
I don't think you should try to mug up all 24 names instead you should keep getting familiar with them when they come in reactions or somewhere else. After seeing them at few different places you will be remember them all. They will come very often while you are learning chemistry.
2 - Yes and no.
It is recommended to known common ions. They are, however, derived in uniform fashion from name of the element in latin. For example, for $Fe$ the name is Ferrum so anions are Ferrates. The 'fancy' part of the anion may consist either of naming the oxidation state (and optionally the number of oxygens and other atoms), i.e. (tetraoxo)ferrate(VI) or known suffixes and prefixes (hypochlorite-chlorite-chlorate-perchlorate, also hydro-, pyro-, orto- and meta- prefixes). Probably the easiest way to remember the second nomenclature would be to learn several (tens of) common ions and assume that isoelectronic ions have same prefixes and suffixed, but are derived from names of respective elements.
In practice, even though the first nomenclature is normative and is understood universally, the second is traditional and more common.
Some oxoions, however, have special names, like dithionite-ion.