Oxidation States of Transition Metals

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  • 0:04 What Is a Transition Metal?
  • 0:28 Oxidation State
  • 2:46 Half Equations & Color
  • 4:32 Lesson Summary
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Lesson Transcript
Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

Transition metals can be a little confusing, but this lesson will simplify things by explaining why transition metals can have more than one oxidation state. It will also touch on other topics such as half equations and colored solutions.

What Is a Transition Metal?

The periodic table is filled with fascinating elements. For example, did you know:

  • Nearly all of the earth's core is made of iron?
  • Vanadium is named after a Scandinavian goddess?
  • People used to use mercury as a cure-all for a whole list of aliments?

What do these elements have in common? These are three of the transition metals found in groups 3 through 12 on the periodic table. These metals have varying oxidation states.

Oxidation State

Oxidation states, (aka oxidation numbers), are numbers that show how many electrons the element would lose or gain if it were to bond to other atoms. For example, iron can have an oxidation state of +3. This means that iron has lost three electrons. Oxygen (which isn't a transition metal) has an oxidation state of -2. This means it would gain 2 electrons. You see, some atoms like to give away their electrons and some like to take them.

  • Oxidation means a loss of electrons. If the oxidation state increases, there's been an oxidation. Or, the atom was a giver.

  • Reduction means a gain of electrons. If the oxidation state decreases, the substances have been reduced. Or, the atom was a taker.

Remember: LEO the lion goes GER. LEO stands for Loses Electrons Oxidation and GER stands for Gains Electrons Reduced.

Now, a lot of the elements on the periodic table are simple. For example, the group 1 elements, also called the alkali metals, have a +1 oxidation state. Alkaline earth metals have a +2 oxidation state. Transition metals, however, are a little complicated.

Electrons are oriented around the nucleus, or the center, of the atom. Some of these electrons are closer to the nucleus and some are further away. Generally, it's easier to take electrons that are further away from the nucleus.

In alkali metals, the electron furthest away from the nucleus can be removed, but it would take too much energy to remove the electrons closer to the nucleus. This is why chemists can say with good certainty that those elements have a +1 oxidation state. It means that chances are, the alkali metals have lost one and only one electron.

However, with the transition metals, there are a bunch of electrons that take about the same amount of energy to remove. It's possible that one electron is removed, but it's also possible two, three, or four could be removed (depending on the transition metal). So, these transition metals can have numerous oxidation states.

For example, iron can be found in several oxidation states such as +2, +3, and +6. Chemists have found a way to let you know the oxidation state of the element by placing a Roman numeral after its name. For example, Iron (II) is iron with a +2 oxidation state.

Half Equations & Colors

Chemists can show the losing or gaining of electrons with half equations. Let's look at an example to get the general idea.

Look at the half equation for the oxidation of iron.


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