Naming compounds?

Question

Which name is incorrect?
BBr- boron tribromide
CO2- carbon dioxide
Na2S- disodium sulfude
PCl5- phosphorus pentachloride
KCl- potassium chloride

The correct answer is Na2S, but I dont understand why it's the right answer. When I looked at this question it seemed like all of the answers were correct.

Yes i did mean to write BBr3 oops

Answer 1

I'm assuming you meant to write BBr3 at the top.

when naming ionic compounds you do not put prefixes in front of the cation or anion (unless the cation is a transition metal in which case you would use a roman numeral). The correct name is simply sodium sulfide, and it is understood that there must be two sodium atoms to balance the -2 charge on sulfur.

Answer 2

If Na2S is the correct answer then maybe it's because of the spelling? 'Sulfide' instead of 'sulfude'?

Seriously, the right way to name a binary metal-nonmetal compound is to name the cation first, which is almost always the metal followed by the anion, the nonmetal. The metal in this case is the Na2 while the nonmetal is the S.

For example: Li2S - Lithium Sulfide --> as you can see, you don't have to put a prefix on the metal.

So for Na2S, it's correct name should just be Sodium Sulfide.

Here is a link of website where they give examples on how to name compounds correctly. They even have Sodium Sulfide. Try to read since I didn't elaborate more.

http://chemsite.lsrhs.net/Equations_and_Formulas/naming_ionic.html

P.S. I didn't look at the other choices. :)

Answer 3

BBr3 = boron tribromide
correct
corrrect
correct
correct

Sorry. You were wrong.