[Saamic]

Hey I just started my studies in chemistry and I'm currently doing my AP chemistry summer assignment and I learned how to name compounds just a few days ago, but now I'm a bit confused. I was learning about cations and anions and I was asked to name the compound H2S. I said it was dihydrogen sulfide but although I was technically correct, the more commonly used name is hydrogen sulfide. Why is this so?

[Saamic]

Sorry nevermind I continued to read my book at it said that when hydogen is metioned in a formula it is almost always meant to be a diatomic molecule of hydrogen

[Saamic]

So instead I'd like to ask why are hydrogen, nitrogen, and the halogens found more commonly in their diatomic form in nature?

[gertrudetrumpet]

the covalent bonding between the atoms creates a full valence shell and increases stability.

[Schrödinger]

Octet in the case of N2, O2, Cl2, etc and doublet in the case of H2.

[vmelkon]

Sorry nevermind I continued to read my book at it said that when hydogen is metioned in a formula it is almost always meant to be a diatomic molecule of hydrogen

Sounds like you are confusing H2S with H2.

diatomic molecule of hydrogen means H2 which is a H atom bonded to another H atom.

In H2S, there is no bond between the H atoms.
Naming conventions dictate that it get called dihydrogen monosulfide just like for water = dihydrogen monoxide.
http://en.wikipedia.org/wiki/Dihydrogen_monoxide

but normally people call them hydrogen sulfide and hydrogen oxide.
There are a lot of other cases like that.

[Schrödinger]

The main reason for the convention is that hydrogen's valency is one ALWAYS. And sulfide is a reference to the -2 oxidation state of sulphur. So, hydrogen sulphide can mean only one thing, because there is only one SULPHIDE of HYDROGEN.

Take in contrast the case of the oxides of nitrogen. NO, NO2, N2O, N2O4, N2O5. Here there is a need to specify the valency of each element explicitly in the name. Nitric, nitrous, dinitrogen pentaoxide, etc

[vmelkon]

The main reason for the convention is that hydrogen's valency is one ALWAYS. And sulfide is a reference to the -2 oxidation state of sulphur. So, hydrogen sulphide can mean only one thing, because there is only one SULPHIDE of HYDROGEN.

Take in contrast the case of the oxides of nitrogen. NO, NO2, N2O, N2O4, N2O5. Here there is a need to specify the valency of each element explicitly in the name. Nitric, nitrous, dinitrogen pentaoxide, etc

It depends. When I was taking courses at school, if you dare to name such as compound hydrogen sulfide, you get 0.
The book says you must prefix each of them.

As for the nitrogen oxides, let's take NO2 as an example. I've seen it called nitrogen dioxide. You get a zero.
N2O, you might be tempted to call it dinitrogen oxide and you get a 0 for omitting the "mono".

As for H2. You call it hydrogen and you get 0. They want you to write dihydrogen.
Cl2. You call it chlorine and you get 0. They want you to write dichlorine.

For some bizarre reason, helium is helium, neon is neon, ...and not monohelium. Weird.

[Fluoroantimonicacid]

The main reason for the convention is that hydrogen's valency is one ALWAYS. And sulfide is a reference to the -2 oxidation state of sulphur. So, hydrogen sulphide can mean only one thing, because there is only one SULPHIDE of HYDROGEN.

Take in contrast the case of the oxides of nitrogen. NO, NO2, N2O, N2O4, N2O5. Here there is a need to specify the valency of each element explicitly in the name. Nitric, nitrous, dinitrogen pentaoxide, etc

It depends. When I was taking courses at school, if you dare to name such as compound hydrogen sulfide, you get 0.
The book says you must prefix each of them.

As for the nitrogen oxides, let's take NO2 as an example. I've seen it called nitrogen dioxide. You get a zero.
N2O, you might be tempted to call it dinitrogen oxide and you get a 0 for omitting the "mono".

As for H2. You call it hydrogen and you get 0. They want you to write dihydrogen.
Cl2. You call it chlorine and you get 0. They want you to write dichlorine.

For some bizarre reason, helium is helium, neon is neon, ...and not monohelium. Weird.

If I took this exams, I would swear,I think. What a stupid thing. H₂S is hydrogen sulfide,and NOCl is nitrosyl chloride.
Did they want you to name CH₃Cl monocarbon trihydrogen monochloride instead of methyl chloride?

[vmelkon]

I'm not sure what their point was. Everyone knows by heart that hydrogen gas is H2. If you read the book, you'll know. Also, no need to put "mono" in front of everything ; example : CO and CO2 where we don't start it with "monocarbon".
CCl4 is carbon tetrachloride. There aren't any dicarbon tetrachloride and any other versions of it.

It's all about knowing it by heart. Or just, draw the molecule and know how the atoms connect.

If someone calls CH3Cl carbon trihydrogen chloride, I can guess how many C and Cl there are.

[sjb]

I'm not sure what their point was. Everyone knows by heart that hydrogen gas is H2. If you read the book, you'll know. Also, no need to put "mono" in front of everything ; example : CO and CO2 where we don't start it with "monocarbon".
CCl4 is carbon tetrachloride. There aren't any dicarbon tetrachloride and any other versions of it.

No dicarbon tetrachloride? What about perchloroethylene? Or, if you want tricarbon tetrachloride - 1,2,3,3-tetrachlorocycloprop-1-ene (perhaps a bit of a stretch, pun not intended)...?

[fledarmus]

This is one of those things that depends very strongly on who is teaching the course and how strongly they feel that their way is the only proper way. Style guides from various journals helped to exacerbate the issue, and the difficulties of cross-indexing common names with everybody's personal preference on "systematic" nomenclature has made it a nightmare. The important thing is that the structure of the molecule should be clearly apparent from the name. Unless you're really working with exotic materials, names like hydrogen sulfide, sodium carbonate, and hydrogen identify unique chemical structures. Iron oxide, nitrogen oxide, and palladium chloride do not. So if your teacher counts your name wrong, ask yourself (and/or your teacher) if there is any other reasonable structure that your name could represent. If not, the name should be acceptable.

Just don't tell your teacher that I said so :-)

[vmelkon]

I'm not sure what their point was. Everyone knows by heart that hydrogen gas is H2. If you read the book, you'll know. Also, no need to put "mono" in front of everything ; example : CO and CO2 where we don't start it with "monocarbon".
CCl4 is carbon tetrachloride. There aren't any dicarbon tetrachloride and any other versions of it.

No dicarbon tetrachloride? What about perchloroethylene? Or, if you want tricarbon tetrachloride - 1,2,3,3-tetrachlorocycloprop-1-ene (perhaps a bit of a stretch, pun not intended)...?

Good point. I guess you could call it dicarbon tetrachloride if you really wanted.

sodium carbonate, Iron oxide

These ones are fine since there is a rule and everyone obeys it.

I just have a problem with the silly ones like "dihydrogen" and "monocarbon dioxide".