RedOx reactions

In our lesson on Sunday we covered 2 definitions of Oxidation and Reduction reactions

One view of oxidation is the gain of oxygen another view is that it's the loss of electrons

One chemicals loss of electrons is another chemicals gain so oxidation and reduction happen at the same time. Hence the Reduction - oxidation name cos it's a two way thing. The electrons thing is quite confusing because it doesn't involve oxygen and the name of the process is oxidation.

Oxidation is easy to remember when oxygen is involved as it's obvious that a gain of oxygen is an oxidation and a loss is a reduction. That much is obvious. With electrons the process is the opposite hence the OILRIG acronym to help you remember the process for electrons

Now a little insight into what's going on here. You need to know a little about ions and the convention for writing them. As you know if an ion has a positive charge it's written with a little "+" sign up top after the number. We know that if it loses one electron it becomes + and if 2 electrons are lost it becomes 2+, 3 electrons 3+ etc, e.g Li goes to Li+, Mg to Mg2+ etc
That number up top is related to it's combining power and it's got a number of names...
Valency
oxidation number
ionic charge
...and there are more names on the redox sheet you got on wednesday

But notice that it's also called oxidation number

So anything that changes the oxidation number positively is an oxidation. rememebr that Losing a negative (electron) is like gaining a +. It's a messy state of affairs but losing an electron (single negative) has the same effect ON THE CHARGE as gaining an oxygen ION (single positive) so from an ionic point of view it is exactly the same. Yeah that used to do my head in as well!

So if there is a change in the valency of the reacting chemicals it's technically, by our definition of redox reactions, a redox reaction.

Take a look at http://www.chemistry.co.nz/redox_new.htm (it would be helfpul just to look at the bits in the boxes - copy them out into your book if you need to - I don't mind you writing abything into your book if it helps you learn) - Also click on the links at the top of that page for more info on how to get the valencys and a bit more info on ionic equations and a few examples.