It is NOT Molybdenum Disulfide

[Nick R]

Everyone's been saying it wrong for years. Because of the fact that Moly is a metal, the Moly and Sulfur bond ionically. Ionically bonded molecules do NOT get prefixes. The correct name would be MoS2 or Molybdenum (IV) Sulfide. The Roman numeral IV is the oxidation number of the moly.

 

[dsmith41]

Thank you. I can sleep now.

 

[tom slick]

Interesting, got a link or some other info on how we've got it wrong?

 

[yeti]

it's not every day that car guys can be corrected by a high school SENIOR, who's maybe 17 yrs. old.i have callouses older than you. just for showing disrespect to your elders, you're in time out !no dessert for you, young man ! have a happy thanksgiving, kid.

 

[addyguy]

Yeah, there are tribologists on here that have been working in the industry longer than you've been alive!

I'm sure there degrees and PHD's just taught them wrong, though!

Good luck making friends here with THAT attitude!

 

[vxcalais]

Originally Posted By: addyguy
Yeah, there are tribologists on here that have been working in the industry longer than you've been alive!

I'm sure there degrees and PHD's just taught them wrong, though!

Good luck making friends here with THAT attitude!


Does not mean they were right either.....they may have just purposely downgraded the terminology for us simpletons gone with the flow and used what they believed we were used to. It is the net after all, being blamed for poor spelling and grammar of society and future generations.

 

[Nick R]

Trust me, we just did an entire unit in chemistry about oxidation numbers and bonding. Only non-metals can bond molecularly (covalent), when you bond a metal and non-metal (metals cannot bond) you get ionic bond. I will see if I can find a link, but for now I ask that you take my word for it. I have nothing to gain by making it up and did not post this to cause trouble. Simply that they named it wrong. Molybdenum is a metal. Sulfur is a non-metal. When they bond, it's an ionic bond. Ionic bonds do not get prefixes, they get roman numerals for the oxidation number of the metal.

This is the best I can find for now. I'll try to scan the stuff we've done.
http://www.angelo.edu/faculty/kboudrea/general/formulas_nomenclature/Formulas_Nomenclature.htm

 

[Nick R]

I'll show you. According to the Periodic table, Molybdenum is a metal, and sulfur is a non-metal.

Blue=metal
yellow=non-metal
red=metalloid

Molybdenum= Mo (#42)
Sulfur= S (#16)

http://intro.chem.okstate.edu/1215SP2000/Lecture/Chapter4/Lec2113.gif


Metals and non metals bond ionically. Neither Mo or S2 is a polyatomic ion, so that eliminates that possiblity.
http://en.wikipedia.org/wiki/Ionic_bond


The oxidation numbers of Molybdenum are +4, and +6. The oxidation numbers of Sulfur are -2, +2, +4, and +6. When all is said and done, the oxidation numbers of molybdenum and sulfur will cancel and equal zero. So, Mo=+4, and 2x -2= -4. So in this compound moly=+4, and Sulfur=-2. 4+ (2x -2)=0 And since it is an ionic bond, nomenclature eliminates prefixes, and the metal comes first. The oxidation state of the metal is stated in roman numerals, after the metal, and in this case is +4. So it will look like this. Molybdenum (IV) Sulfide. The oxidation number is stated, and you would be able to find the oxidation number of sulfur from this equation. So MoS2= Molybdenum (IV) Sulfide. If moly was a non-metal, then it would be monoMolybdenum Disulfide. (Water is actually called DiHydrogen Monoxide)

EDIT: I cannot imagine why they would intentionally name it wrong. MAybe it was just a mistake, and it stuck.

 

[Pablo]

Or maybe IUPAC changed naming protocol somewhere in the past.

 

[Nick R]

I hadn't thought of that pablo.

 

[Petrou]

MOLY MOLY MOLY MOLY MOLY

SORRY I HAD TO PULL AN AUSTIN POWERS MOMENT, IT WAS GREAT SETUP.
THANK YOU FOR FOR BEING EXACT, AND ITS GOOD TO KNOW

 

[GMorg]

The OPs question can be useful in this forum. I have three points. The third one is worth considering at BITOG.

1. molybdenum disulfide, molybdenum disulphide, and Molybdenum(IV) Sulfide are all names of the same compound. It is like saying that the terms "cane sugar" and "sucrose" are wrong because standard chemical nomenclature also allows the same molecule to be called either alpha-D-Glucopyranosyl-beta-D-fructofuranoside or with equal validity beta-D-Fructofuranosyl-alpha-D-glucopyranoside.

2. There is a difference between "wrong" and "different from your current understanding."

3. You may want to consider that Mo is a transition metal. Unlike the main group metals, the transition metals are more electronegative and can share valent electrons more easily than the main group metals. When a bond is created due to sharing valent electrons it is referred to as "co-valent." This is an important concept when you think about the chemistry that occurs when Zinc dithiophosphates react on a bearing surface. Why is so much heat required for a bond to form with iron if it can only form ionic bonds? And, why don't ZDDPs react with the main group metal aluminum? Could it be that transition metals are more likely to form covalent bonds? Categorization of the periodic chart is handy, but it is not absolute.

 

[lipadj46]

There are different naming conventions and people who took chemistry in high school before they dumbed down the curriculum (talking New York State Regents here) would have learned it as molybdenum disulphide now they learn the latest IUPAC naming convention which would be molybdenum (IV) sulphide.

 

[jhenle]

Originally Posted By: rudolphna
Trust me, we just did an entire unit in chemistry about oxidation numbers and bonding. Only non-metals can bond molecularly (covalent), when you bond a metal and non-metal (metals cannot bond) you get ionic bond. I will see if I can find a link, but for now I ask that you take my word for it. I have nothing to gain by making it up and did not post this to cause trouble. Simply that they named it wrong. Molybdenum is a metal. Sulfur is a non-metal. When they bond, it's an ionic bond. Ionic bonds do not get prefixes, they get roman numerals for the oxidation number of the metal.

This is the best I can find for now. I'll try to scan the stuff we've done.
http://www.angelo.edu/faculty/kboudrea/general/formulas_nomenclature/Formulas_Nomenclature.htm


LOL

I wish chemistry were as simple and clean-cut as you picture it here.

It's not.

Molybdenum is a metal, yes. But it's a transitional metal, and that's what makes a difference. Transitional metals tend to have extra electrons sitting parked in weird orbitals, and these electrons can be convinced, rather easily, to share themselves with other atoms that happen to be nearby, sometimes of an opposite chemical orientation that the metal in question... in other words, bonds made by transitional metals are not as clean-cut ionic that the ones made by say alkaline metals. They are prone to making (Oh the shock! The shame!) covalent bonds.

Also, some non-metals that have a less non-metallic character than other, more electronegative non-metals, are known to be easier approachable by transitional metals to form (The shock! The shame!!) covalent bonds with them. Case in point: carbon, and all the organometallic compounds. Or maybe that's the next chemistry module you'll be taking.

To drive the point home: I wouldn't be so quick to say "MoS2 is definitely an ionic compound, and it should thus be named such and such" without bringing some evidence. In fact if you run a quick search, there is strong evidence to suggest that the Mo-S bond is part ionic, part covalent.

(edit) BTW, you say, quote "The oxidation numbers of Sulfur are -2, +2, +4, and +6"
Have you given any thought on how can sulfur, a non-metal, have positive oxidation states? What do these exactly mean?

--jhenle, PhD

 

[lipadj46]

Originally Posted By: rudolphna
Trust me, we just did an entire unit in chemistry about oxidation numbers and bonding.


Trust me, I have taken nearly 6 years of chemistry classes and teach chemistry and I don't pretend to be an expert. Your one unit on bonding is just scratching the surface and many of the things that were taught to you were gross simplifications (that get corrected as you get into higher level chem classes).

 

[Gary Allan]

Sometimes you learn just enough that you don't realize that you haven't learned enough. At some point you figure that part out too ..but it's further out as your expanding knowledge circle/bubble reaches a level of incompetence.

This is usually where I tell someone to earn their fortune NOW while they still know it all ..but that could sound rude.


rudi: this is a place where you'll get spanked ..and quick ...if you're sticking it out there. There's many smart people here. You hang it out there, someone can surely lop it off for you.

Now, OTOH, if you had started off: "Why is this the way it is? I just went through this torture and it seems that what I learned is counter to convention. Why is that?

" ..then I think it would have been different.

Then again, if you can take getting spanked ..carry on. It never stopped me

 

[mechtech2]

Who says all moly oil additives must bond?
Are we certain some simply don't slip and slide against each other without bonding to metals?

 

[GMorg]

I don't think that anyone said that all moly additives must bind.

 

[Nick R]

I'm mature enough to admit I was wrong. We were simply taught that. In hindsight, I can see how they would simplify it for the high school course. By the way we were taught it WAS wrong, but if moly can bond molecularly, then I guess it would be moly disulfide.

 

[mechtech2]

G Morg - Read the first post for the answer to your question.