Confused

[Banks]

I'm trying to figure out the name for this formula, Cu(bottom 2)S, would it be called Copper (II) Sulfide or just Copper Sulfide?

 

Seeing that Copper has two charges, 2+ and 1, and Sulfur has only 2-.

 

Thanks!

Edited February 18, 2012 by Banks

[hypervalent_iodine]

You would usually write it with the charge in brackets, though it is sometimes not necessary. Your example makes it clear that the oxidation state is +2, so you wouldn't have to write (II), but it is just as correct if you do.

[Suxamethonium]

Sorry. Wouldn't Cu₂S be copper (I) Sulfide? CuS would be copper (II) sulfide.

[elementcollector1]

You would usually write it with the charge in brackets, though it is sometimes not necessary. Your example makes it clear that the oxidation state is +2, so you wouldn't have to write (II), but it is just as correct if you do.

 

Wait, wouldn't copper be in the 1+ state in this compound?

2 Cu+ + S2- = Cu2S, right?

For copper to be +2, it would be CuS.

[hypervalent_iodine]

I didn't read what he had in brackets. Yes, you're right.

 

Banks, when you write posts you'll notice that the bar that gives you options to bold, underline, etc., also gives you the function to sub and super script. They are the X₂ and X² buttons, respectively.

[Banks]

So, Cu₂S would be called Copper (I) Sulfide? Why would CuS be called Copper (II) Sulfide?

 

Why? Would I have to figure out some ratio for both elements?

 

Sorry, I'm trying not to be confused and am attemping to see a pattern here...

 

Thanks for replies, gentlemen.

Edited February 18, 2012 by Banks

[hypervalent_iodine]

The I and II describe the oxidation states of the copper. Copper (II) is Cu²⁺ and copper (I) is Cu⁺. You can tell the oxidation states by treating the whole thing as an algebraic expression. In the case you've listed, the net charge of the complex is 0, which means that the sum of the charges of the constituents must sum to 0. We can assume that the sulphur has an oxidation state of 2-, which makes the equation

 

0 = x - 2 (where x is the oxidation state of the copper)

 

Rearranging that gives x = 2, so the copper in CuS must have a +2 oxidation state.

 

For Cu₂S, we have:

 

0 = 2x -2

2 = 2x

 

Which then gives us x = 1, so in this case our copper must have an oxidation state of +1.

 

Ligands such as water, ammonium, cyano groups, etc., all have fairly well-defined defined charges. Water is neutral, ammonium has a +1 charge, cyanide has a -1 charge, etc., etc. Sulphur tends to be a bit tricky in cases like this, as it can exist in quite a number of oxidation states due to its ability to form hypervalent bonds; in this case, however, the copper monosulphides will have S^2-.

 

Also, as an aside, I'm not a gentleman

[Banks]

In my textbook, given example, it says:

 

Write the name of the compound that has the formula Cu₃N_(s).

 

1. Identify the ions that form the compound

 

Cu^? copper ion, N^3- nitride ion

 

2. Use the charge of the nitride ion (3-) and the rule that the total positive and negative charges in the formula unit must be equal. Three copper ions are present in the formula unit so each must have a charge of 1+.

 

3. Write the name of the compound.

 

The name of the compound is copper (I) nitride.

 

So, according to #2, I don't get the "rule", how would I determine this? How are three copper ions are present in the formula unit?

 

Does it go something like this...

 

N^3-: 3

Cu⁺: 1+1+1=3

 

Therefore, ratio is 1 to 3 or 3 to 1....therefore copper (I) nitride?

 

In the periodic table, Copper element has two charges, of 1+ and +2, so +2 is out of the question because it does not match up to 3 (equal to Nitrogen's charge), therefore +1 is applicable.

 

Am I right?

 

I fucking can't still figure out PbO_2, originally I wrote lead (II) oxide, because I saw the number "2" and assumed it would have to be switched to left side. However, in textbook answers it says "lead (IV) oxide", why is this?

 

What's the rule I have to follow? Can anyone explain to me please?

 

Thanks....

Edited February 18, 2012 by Banks

[hypervalent_iodine]

In my textbook, given example, it says:

 

Write the name of the compound that has the formula Cu₃N_(s).

 

1. Identify the ions that form the compound

 

Cu^? copper ion, N^3- nitride ion

 

2. Use the charge of the nitride ion (3-) and the rule that the total positive and negative charges in the formula unit must be equal. Three copper ions are present in the formula unit so each must have a charge of 1+.

 

3. Write the name of the compound.

 

The name of the compound is copper (I) nitride.

 

So, according to #2, I don't get the "rule", how would I determine this? How are three copper ions are present in the formula unit?

 

Does it go something like this...

 

 

It tells you in the question how many copper atoms are present, so all you have to do is solve for x the same way I did in my previous post. The net charge of the molecule is 0, so again we have:

 

0 = 3x -3 (3x because there are three copper atoms in the formula)

 

3 = 3x

 

Which gives us x = 1, i.e. Cu⁺_. So we have 3 coppper atoms, all with a +1 oxidation state, and a central nitrogen with a -3 charge.

 

 

I fucking can't still figure out PbO_2, originally I wrote lead (II) oxide, because I saw the number "2" and assumed it would have to be switched to left side. However, in textbook answers it says "lead (IV) oxide", why is this?

 

What's the rule I have to follow? Can anyone explain to me please?

 

Thanks....

 

As much as I hate to promote this sort of learning, there are some things that you just have to remember. Unless in their elemental form, hydrogen exists in a +1 state, oxygen is -2 (unless it's in a peroxide, in which case it is -1) - there are a few. Take a look at this wiki page. It should help. Again, you would treat this question algebraically:

 

0 = x + 2(-2)

0 = x - 4

 

Giving x = 4, which makes our lead Pb (IV), or Pb⁴⁺.