Chem SL - Reactivity Series

[CommeDesEnfants]

For whatever reason, I simply cannot wrap my head around reactivity series. My train of thought begins with, "Okay, so X can oxidize Y, but Y is oxidized by Z... So would X oxidize Z?... Uhhh..."

Yeah. Anybody got any tips for this? :/

[Sonneteer_Trombonist]

I say think of it like a hierarchy on the playground, where the element that most easily gives up electrons is the weak little kid on the playground (the "weakest" element) and the one that takes electrons most easily is the playground bully (the "strongest" element). So the weakest element is oxidized by any of the bullies on the playground, and the strongest bully does the oxidizing, so he is always reduced. Think of it like a line-up where an element can oxidize any elements lower than him and can be oxidized by and elements higher than him, like how a bully can take a ball from any of the weaker kids but if there is a stronger bully he will have the ball taken away. So if we have W as the weakest, X as a mild bully, Y as a fairly strong bully and Z as the strongest bully of all, then W is oxidized no matter what he does, X can oxidize W but is oxidized by Y and Z, Y can oxidize the lower things but is oxidized by Z, and Z oxidizes everything.

And looking at your question, if X can oxidize Y, then X is the bully. If Y is oxidized by Z, then Z is the bully. We don't have enough information to state whether X or Z is the stronger bully here, so we can't say which one is oxidized.

[Sandwich]

I always figured it that the most reactive metals were the strongest, toughest, most hardy ones which could put up with being incomplete the best. Incomplete as in an incomplete electron ring -- they're going to form the positive ions in any reaction between two metals, and are going to have incomplete outer electron rings.

So if you have something like Aluminium facing off against Copper, the one which is going to end up in solution (i.e. as a positively charged ion) is the more reactive one ('cause relatively it has buns of steeeel). However if the ultimate in strong metals, K, came along, it would knock Al out of the spot and become the positive ion because (to help you think of it ) it's trying to prove how awesomely tough it is to be able to last out without a complete electron ring.

Or you can go with the bully thing As sonneteer_trombonist said, there's not enough info to answer your question. If they ever ask you about it, they'll probably give you a series of displacement reactions (that's the whole one metal being solid and the other in aqueous solution scenario) and you have to divine from that the reactivity series. Now that you know the hardest, toughest metal is the one which shows off by putting up with being a positive ion (the metal equivalent of showing off its muscles xP) and so will naturally be the one in solution combining with the negative ions to make the metal salt, it's easy to divine a reactivity series.

[CommeDesEnfants]

Hehe, thanks for the tips. The bully one is.. interesting. I realized that it's a lot more clear to see which one is the strongest/weakest by creating inequalities and looking at them from there.