# Does the term 'silver nitrate' express all of its constituent chemical elements?

My professor gave my class a set of practice questions for the mid-term. One of those questions asks for the molar mass of a number of chemicals, such as lithium bromide and silver nitrate. We haven't studied those chemicals, so there's little reason for the professor to expect us to have memorized the elements that constitute those chemicals. In the case of lithium bromide, the term informs us of its constitution. Whereas,'silver nitrate' informs us that the chemical $\mathrm{AgNO_3}$, includes silver and nitrogen, but I don't see anything in the term that would inform the reader that the chemical includes $\mathrm{O_3}$.

Is there anything in the term 'silver nitrate' that would inform a reader that the chemical includes $\mathrm{O_3}$?

More generally, is there a set of rules that relates the chemical constituents of chemical substances to the linguistic constituents of the terms that designate them?

• Nitrate ions are $NO_3^{-}.$ Nitrite ions are $NO_2^{-}-.$ – Gokul May 23 '15 at 12:03
• chemed.chem.purdue.edu/genchem/topicreview/bp/ch2/… – user15489 May 23 '15 at 12:16
• Chemists will create nomenclature wherever necessary to avoid ambiguity, unfortunately sometimes to the point that systematic IUPAC names can get very unwieldy. But there's nothing we can do about it, chemical space is enormous and extremely varied. – Nicolau Saker Neto May 23 '15 at 12:24

You should know that nitrate is a polyatomic ion with the molecular formula $\ce{NO3^-}$. For example:

Sulfate is a polyatomic ion with the molecular formula $\ce{SO4^{2-}}$; Sulfite is a polyatomic ion with the molecular formula $\ce{SO3^{2-}}$;

Nitrate is a polyatomic ion with the molecular formula $\ce{NO3^-}$; Nitrite is a polyatomic ion with the molecular formula $\ce{NO2^{-}}$

At first glance, the nomenclature of the polyatomic negative ions seems difficult. When the name of the ion ends in either -ite or -ate:

• The -ite ending indicates a low oxidation state.
• The -ate ending indicates a high oxidation state.

I agree with you that at the beginning, it seems difficult. But by practicing, you find this quite easy.

For $\ce{AgNO3}$, as Gokul said in the comment, ‘nitrate’ stands for $\ce{NO3-}$. Sodium nitrate is $\ce{NaNO3}$, ammonium nitrate is $\ce{NH4NO3}$, and so on. It is important to know that $\ce{AgNO3}$ is an ionic compound with ionic bond between $\ce{Ag+}$ and $\ce{NO3-}$, while nitrogen and oxygen in $\ce{NO3-}$ are bonded with covalent bond.

There are conventions for names of compounds. Some convention such as IUPAC name for organic molecule is strict and not so confusing. For ionic compound, there are rules but there are also irregularities. In this case for anions with oxygen, here are some examples:

nitrite $\ce{NO2-}$, nitrate: $\ce{NO3-}$

phosphite $\ce{PO3^3-}$, phosphate: $\ce{PO4^3-}$

sulfite $\ce{SO3^2-}$, sulfate: $\ce{SO4^2-}$

Roughly speaking, ion with the highest oxidation state of central atom got -ate name, while the second highest got -ite.

However, if central atom is in group VII, the naming convention strangely change to:

chlorite $\ce{ClO2-}$, chlorate $\ce{ClO3-}$, perchlorate $\ce{ClO4-}$

bromite $\ce{BrO2-}$, bromate $\ce{BrO3-}$, perbromate $\ce{BrO4-}$

There are also confusing things such as nitride ($\ce{N-}$), nitrile ($\ce{-CN}$), and nitrite ($\ce{NO2-}$).

In practical, it is easier to memorize the name of common ion and search the internet for the name of uncommon ion, rather than messing with confusing rules. I do this all the time when I do chemistry researches. However, this tactics might not work if you have to take a chemistry exam.

• A small correction: the nitride ion is a trianion, $\ce{N^{3-}}$, which itself is not to be confused with the azide ion, $\ce{N_3^{-}}$ – Nicolau Saker Neto May 23 '15 at 17:33