Learning about Oxides. Basically when oxygen is combined with a metal.
$$\ce{FeO}$$
This is called "Iron Oxide (II)" according to my book.
Apparently, the II represents the valence. But how come? Look:
$\ce{Fe}$ has the configuration $1s^22s^22p^63s^23p^6\color{red}{4s^2}3d^6$. Since the outermost shell has $2$ electrons, the valence is $2$.
Now $\ce{O}$ has the configuration $1s^2\color{red}{2s^22p^4}$. Its outermost shell has $6$ electrons so oxygen has a valence of $6$ right?
Then how come $\ce{FeO}$ has valence $2$? Shouldn't the valence of $\ce{FeO}$ be like, the combination of the two valences? So $6 - 2 = 4$? (I read somewhere you had to subtract it).
Not only that. I am starting to think that my definition of valence is completely messed up. I just checked in here and apparently Oxygen has $-2$ valence? Why? And Iron has +2, +3, (+4), (+6)? What does all that even mean?
Answer
Ok, finding valencies of elements in simple compounds is very easy, but you have to know some thing to start:
You are treating compound as if it would be composed of discrete molecules
If you have compound/neutral molecule, sums of valencies of both types of atoms should be equal, as valency is number of bonds between atoms.
In case of FeO you need to know that O make usually two bonds (valence = 2) and as both valencies have to be equal Fe also has val = 2
In case of Fe2O3, 3*2=6, 6/2=3 so Fe is trivalent.
No comments:
Post a Comment