Transition Metal Cations

So far, we have only discussed 4 families of elements: the alkali metals, the alkaline earth metals, the halogens, and the noble/inert gases.  Now we are going to pay attention to all those elements in between!

Take a look at groups 3 to 12.  They are all metals, right?  Well, we group these elements into a category called the "transition metals."  This isn't a chemical family; in fact, transition metals really only have a few things in common:

1) They are all metals
2) They all have 4 or more electron orbitals (these are called d-orbitals)
3) They all form cations in ionic compounds

Because of their unique d-orbitals, these transition metals don't follow the same patterns of other metals we've learned about.  It is difficult to predict what cation a transition metal will form and some transition metals can form two different cations!  Let's break it down...

• Take a look at your Periodic Table of the elements.  Can you identify the transition metals?
• Find the element iron (period 4, group 8).  You may notice that there are two integers included in its cell.  +3, +2.  These integers represent the cations that iron can form in an ionic compound.  So, you could have Fe3+ or Fe2+.  This means that iron can give away 3 valence electrons (Fe3+) or two valence electrons (Fe2+).  What are the two cation charges for palladium (period 5, group 10)?

• You'll notice that some elements only form one cation (Zn2+, for example) and that others form two (Cu2+ or Cu1+).  If there are two possible cations, the first integer represents the cation it is most likely to form.

So, take a look at the following two examples and see if you cannot determine which cation of iron is used in each:

1. FeO
2. Fe2O3

Figure it out?  First thing you should ask is "what is the charge of the anion?"  Oxygen has 6 valence electrons and can receive two more.  Therefore, in an ionic compound, oxygen is always O2-.  Now you have to figure out the charges of the cations which will create a stable (no charge) ionic compound.

1. Fe2+  and O2-  will create FeO
2. 2 x Fe3+ (total positive charges = 6) and 3 x O2- (total negative charges = 6) will create Fe2O3

More about transition metals:

• http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/patterns/transitionmetalsrev1.shtml  (please note that this website labels the groups on the periodic table different from what we have been learning.  Transition metals are in groups 3-12.)
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