Question

3. Write the valency and chemical formula of
a) Fe2 S3​

Answer 1

Answer:

First you should determine where Fe (iron) is on the periodic table. It’s element 26 and it’s right in the middle of the transition metals. Since it’s in the transition metal section of the table you’ll need to assign it a roman numeral for it’s charge (we’ll get to how later) or use a -ic or -ous suffix depending on the method you’re using to name.

Now that we know iron is a transition metal, we have to determine what the other part is. S is element 16: sulfur. All anions (negative ions or those elements that come at the end of an ionic compound) receive the suffix -ide.

So far we have iron () sulfide. Now we just need to fill in the parenthesis with the roman numeral I mentioned before. This number is indicative of the charge that the iron has.

All ionic compounds need to be neutral or have a zero net charge. That means we can add all the positive charge and negative charge and know it will give us a total of zero:

(# of positive ions)(charge of positive ions) + (# of negative ions)(charge of negative ions) = 0

So we have 2 iron and we don’t know it’s charge so we’ll call it x:

(2)(x) + (# of negative ions)(charge of negative ions) = 0

We have 3 sulfur and from the periodic table we know its charge is -2 (S is a group 6A element and needs to gain two electrons to reach an octet of valence electrons). This gives us:

(2)(x) + (3)(-2) = 0

Now we solve for x:

2x - 6 = 0

2x = 6

x = +3

So the number 3 goes in the parenthesis from before! BUT WAIT! It needs to be a roman numeral, so recall 3 = III. This gives us the final name of:

iron (III) sulfide [this is sometimes written as just iron III sulfide]

and that’s the name in the Stock system (the more modern naming system).

The classical name is ferric sulfide. This is a poor naming convention because it requires you to know that ferric = iron (III) and ferrous = iron (II). [You would need to know every possible charge for all of the multiple charge state elements to fluently use this system. This is why the Stock system is preferential. You only need to understand the system to determine a formula or name].

Hope that helps

Answer 2

Answer:

iron hahahhhhhhhhhhhhhaaaaaaaaaaaaa fff