How do you write the formula for these compounds containing polyatomic ions?

the compounds are: sodium perchlorate, calcium acetate





i kno the symbol for sodium and calcium but how do you or where can you find the symbol for perchlorate and acetate?

i hav searched the whole book...which is Prentice hall chemistry textbook



also, is this right?

chromium (III) nitrite = Cr(NO3) the 3 is small and is on the bottom



thanks for helping me clear my confusion. smorgle.How do you write the formula for these compounds containing polyatomic ions?
perchlorate is ClO4 (with -1 charge) acetate is the same as ethanoate its CH3COO- with -1 charge

sodium perchlorate is NaClO4 and sodium acetate is CH3COONa



NO3 is nitrate (with -1 charge)

nitrite is NO2 (also with -1 charge)



chromium (III) nitrate is Cr(NO3)3 (3 nitrates)

chromium (III) nitrite is Cr(NO2)3