It's far to taxing to write all of the rules of nomenclature on this board; however, I can give you some starting points and give you a link or two to read.
First, for salts, name the cation first and the anion second. http://www.woodrow.org/teachers/chemistry/links/chem1/PolyatomicIonsChart.htmls
Na3PO3. Na is sodium, name that first. PO3 is the phosphite ion so the salt is sodium phosphite.
AuNO2. Au is gold. Since gold has common oxidation states of +1 and +3, it can be named gold(I)nitrite. Etc.
Don't get discouraged. It takes a lot of practice. I recommend you memorize the anion tables and some of the common acids. There are rules for naming them but memory gets you started in hurry.
First, its Sn and not SN.
Next, tin(IV) means tin with a valence of 4. Dichromate is Cr2O7^2- (I don't know if the dichromate ion is given in the chart I gave you or not).
Sn2(Cr2O7)4 is exactly the answer you would get; however, we USUALLY (not always) reduce the fractions if possible. Since both 2 and 4 are divisible by 2, we have Sn(Cr2O7)2.
(The only time we don't reduce it is when we KNOW the formula is not the simplest empirical formula. For example H2O2 is hydrogen peroxide and not HO. S8 is sulfur and not S. Hg2Cl2 is mercury(I) chloride and not HgCl.)
okay , the website you put does not work. But one last question. for sodium hydrogen arsenate it says to give the correct formula. how do i go about doing that? how do i start?
i know that sodium is Na and that arsenate is AsO4^3-
Does anybody know of a website that explains organic nomenclature ? ...something along the lines "organic nomencluture for Dummies" would be great :-) I'm stuggling to underatand "Z-3-Bromo-6-methyloct-3-ene" let alone draw it !