# Could someone show me how to write oxidation numbers above the element? I saw how Stefan V. did it, but I have forgotten how! Thanks in advance! :)

Dec 7, 2015

You use the "stackrel" function.

#### Explanation:

I learned all the following from our good friend Stefan V.

The syntax is stackrel(oxidation number)(atom).

For example, stackrel(+2)("Cu") without hashtags becomes $\stackrel{+ 2}{\text{Cu}}$ with hashtags.

I usually combine this with the "color" command.

For example, stackrelcolor(blue)(-2)("O") without hashtags becomes $\stackrel{\textcolor{b l u e}{- 2}}{\text{O}}$ with hashtags.

Here's a typical redox equation with oxidation numbers.

$\stackrel{\textcolor{b l u e}{+ 1}}{\text{Cu"_2) stackrel(color(blue)(-2))("S") + stackrel(color(blue)(+1))("H") stackrel(color(blue)(+5))("N") stackrel(color(blue)(-2))("O"_3) -> stackrel(color(blue)(+2))("Cu") overbrace(("NO"_3)_2)^(color(blue)(-1)) + stackrel(color(blue)(+4))("S") stackrel(color(blue)(-2))("O"_2) + stackrel(color(blue)(+4))("N") stackrel(color(blue)(-2))("O"_2) + stackrel(color(blue)(+1))("H"_2) stackrel(color(blue)(-2))("O}}$

As an aside, you can also use stackrel to put conditions over reaction arrows.

For example,

$\text{A-B " stackrelcolor (blue)("heat or hν"color(white)(Xl))(rarr) "A· + ·B}$

Jan 7, 2016

A little info on some spacing issues...

#### Explanation:

I want to show you how to avoid some pesky spacing issues that can be seen when using the stackrel function and arrows in general.

For example, Ernest's last example looks like this

• without the hashtags

"A-B" stackrel( color(blue)("heat or hν"))(rarr) "A· + ·B"

• with the hashtags

$\text{A-B" stackrel( color(blue)("heat or hν"))(rarr) "A· + ·B}$

Notice how the text written on top of the arrow and the arrow itself are not properly aligned. Moreover, the arrow is pushed too close to that $\text{B}$ reactant.

Here's a trick to use to align things properly.

To get more separation between the $\text{B}$ and the tail of the arrow, use quote marks, " ", or color(white)(a). So, in this example, you can write

• without the hashtags

"A-B " stackrel( color(blue)("heat or hν"))(rarr) "A· + ·B"

• with the hashtags

$\text{A-B " stackrel( color(blue)("heat or hν"))(rarr) "A· + ·B}$

Alternatively, you can write

• without the hashtags

"A-B"color(white)(a) stackrel( color(blue)("heat or hν"))(rarr) "A· + ·B"

• with the hashtags

$\text{A-B"color(white)(a) stackrel( color(blue)("heat or hν"))(rarr) "A· + ·B}$

Now for the text. The thing with using stackrel for arrows is that the arrow must take the size of the text written on top of it.

This means that I can extend the arrow a little bit by using white characters on top. You would have

• without the hashtags

"A-B"color(white)(a) stackrel( color(blue)("heat or hν") color(white)(aaa))(rarr) "A· + ·B"

with the hashtags

$\text{A-B"color(white)(a) stackrel( color(blue)("heat or hν") color(white)(aaa))(rarr) "A· + ·B}$

So, in essence, from the editor's perspective, the text written above the arrow is "heat or hvaaa", so the arrow is extended a bit to accommodate those extra "aaa" characters.

You can use this trick for all kinds of things. I like to use it to show shift in equilibrium for Le Chatelier's Principle problems.

For example, I would write something like

• without the hashtags

stackrel( color(white)(aaaa) color(red)("shifts to the left") color(white)(aaaaa) )(larr)

• with the hashtags

$\stackrel{\textcolor{w h i t e}{a a a a} \textcolor{red}{\text{shifts to the left}} \textcolor{w h i t e}{a a a a a}}{\leftarrow}$

And you can make the arrow however long you want by adding more a's

• without the hashtags

stackrel( color(white)(aaaaaaaaa) color(red)("shifts to the left") color(white)(aaaaaaaaaaaaaaaaaa) )(larr)

• with the hashtags

$\stackrel{\textcolor{w h i t e}{a a a a a a a a a a a a a a} \textcolor{red}{\text{shifts to the left}} \textcolor{w h i t e}{a a a a a a a a a a a a a a a a a a}}{\leftarrow}$