[dillydoo]

I have a problem figuring out why some ion compounds won't write how many of the cations there are in the formula.

This makes sense to me; Potassium Sulfide
K⁺ + S^2- = K₂S

But I don't understand why N^3- + O^2- = NO₃^- when It should be N₂O₃?

Even Phosphate makes little sense to me? Like: P³⁺ + 2 O^2- = PO₄^-  when in my head, it should be P₄O₃

The worst part is that I hate myself for simplifying it by thinking of the extra oxide as the "-" charge and I know, most of the time, I only need to add the group numbers together to see whether they're even or not to determine what the charge is, but it was never explained why.

Is it because they've undergone oxidation? If so, why did the 3 in NO₃^- and 4 in PO₄^- move to the end, and the other ion count disappear? I feel I must've missed something really elemental here.

[Borek]

Polyatomic ions are not (internally) ionic. You are mixing oxides and anions produced during dissociation of acids, these are completely different things.

In general we treat both N in NO₃^- and P in PO₄^3- as having oxidation state of +5 - but it doesn't mean there exist an X⁵⁺ cation inside.

[dillydoo]

Our teacher hasn't explained any of that yet, he's been trying to give us a really brief, child-friendly version... (It's year 1 in high school, so it shouldn't be like that, I feel.) And even the books haven't dealt with formula writing yet. I feel like the lectures thus far are either like a summary or backwards in how we're being taught. Whereas I really do appreciate the references and connections he's trying to show us in that manner, I feel like I've fallen behind because I keep getting stuck and wondering why things are that way and when I ask he doesn't want to go into the depths because the others don't follow. He says he doesn't want to go into the formulas yet, so I'm stuck figuring them out on my own.

I was just wondering if there's a collection (online or any books) of the mathematical equations we're using for formula writing? I'm supposing the X^5- is somehow simplified in the equation? For example, because of oxidation, there's a variable that is removed due to simplification - but I'm unsure when that happens in the equation.

[Yggdrasil]

Many areas of chemistry are unlike physics in that they much less on rigorous mathematical derivation and more on a certain chemical intuition.  Most chemists can look at a chemical structure and figure out its properties not through doing any calculations, but through applying knowledge of certain principles that comes from experience learning about and working with chemicals.  An example of such intuition, relating to your examples, is knowing whether the chemical formulas represent covalent substances (in which electrons are shared between atoms) or ionic substanecs (in which electrons are transferred between atoms).  I'd liken it to how chess players can look at a chess board and immediately see things about the chess game that a novice would not be able to see.

You can recognize covalent substances because they involve bonds between two or more non-metals.  For covalent substances, a good way to think about how the bonding might occur is to draw a lewis dot structure.

[Enthalpy]

The equations must balance the number of nuclei and the number of charges. So it should be
2K+S  K₂S
and then, if under some condition S^2- exists, you can put some charges too.