If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

The periodic table - transition metals

The definition of a transition metal, and how to write the electron configuration including examples for Fe and Zn. Created by Jay.

Want to join the conversation?

  • blobby green style avatar for user Posts Only
    Why does Zinc shed electrons from the 4S and not the 3D?
    (17 votes)
    Default Khan Academy avatar avatar for user
    • leaf blue style avatar for user Sabbarish Govindarajan
      If Zinc leaves the electrons from its 3d orbital, then It'll have 4s2 3d8 configuration.
      If Zinc leaves the electrons from its 4s orbital, then It'll have 4s0 3d10 configuration.

      Remember, The half filled and fully filled orbitals are more stable and the elements try to get this configuration. So, since 3d10 is a fully filled orbital, Zinc will leave its 4s electrons and not the 3d electrons.
      (26 votes)
  • piceratops ultimate style avatar for user imroz alam
    why are transition metals generally good catalysts ?
    (12 votes)
    Default Khan Academy avatar avatar for user
    • leaf blue style avatar for user James Ng
      Transition metals usually have a partially filled d-subshell. This allows the reagents to form temporary bonds with the metal and the intra-molecular bonds of reagents are weaken as a result. The weaker intra-molecular bonds require a lower activation energy to overcome. Therefore more molecules have energy more than the activation energy and the reaction rate increases.
      (25 votes)
  • blobby green style avatar for user Mishal Abid
    hg is a transition metal?
    (5 votes)
    Default Khan Academy avatar avatar for user
  • leaf green style avatar for user Ali
    why for Zn and Fe elements you got the 3d why not 4d?or another electron configuration
    (7 votes)
    Default Khan Academy avatar avatar for user
    • piceratops ultimate style avatar for user Just Keith
      That is just the order the d block fills in. The 3d fills in between the 4s and the 4p.
      We cannot just renumber the 3d to 4d because the numbers have meaning (some of which is above this level of study) and so we have to number them the way they are numbered. So, the d block elements back-fill the d subshell of the previous shell.
      (6 votes)
  • blobby green style avatar for user Danny Li
    How you figure out the valence electrons for an element in the d-block?
    (3 votes)
    Default Khan Academy avatar avatar for user
    • piceratops seed style avatar for user RogerP
      In the d-block, valency is not so straightforward as in the s and p blocks. Most of the d-block elements can lose their two s electrons to give a cation with a charge of +2. But when it comes to losing electrons from the d subshell, there are often several possibilities giving rise to cations with different charges.
      (7 votes)
  • aqualine seed style avatar for user Kayla Goble
    So what is the chimerical properties of transition metals?
    (2 votes)
    Default Khan Academy avatar avatar for user
  • leaf green style avatar for user Varun Sharma
    Why are the electrons mapped out in such an orderly way when in reality they just orbit the nucleus in an irregular, elliptical pattern?
    (4 votes)
    Default Khan Academy avatar avatar for user
    • aqualine ultimate style avatar for user Dragoljub Blagojevic
      The simplicity of Bohr's model is easy to explain to those who start studying chemistry, and while the model itself may not represent the true nature of an atom, it portrays a rather simple picture of orbits and energy levels, making the concept of those easier to understand.

      Just think about how it would be like if you were to explain to the kids The Uncertainty Principle :)
      (2 votes)
  • hopper cool style avatar for user Khan academy
    Shouldn't transition metals then be from Group 3 to 11 then as in the case of Zn, Cd, Hg, etc?
    (4 votes)
    Default Khan Academy avatar avatar for user
  • male robot hal style avatar for user ßũƞȞǿ
    so zinc 2plus ion is a transition metal but zinc isn't?
    (3 votes)
    Default Khan Academy avatar avatar for user
  • leafers ultimate style avatar for user ben.ten.study
    Should the 5th period on the periodic table have 24 transition metals?

    Simply because the 4th or previous shell can hold 32 electrons (following the 2n^2 rule; 2*4^2 = 2*16 = 32). Meaning it would take 24 transition metals to complete the shell.
    (2 votes)
    Default Khan Academy avatar avatar for user

Video transcript

In the last video, we saw the classification of elements into groups on the periodic table, and we stopped with the definition for a transition metal. There are two ways to think about transition metals. So one way to think about it would be when some teachers say transition metal, they're talking about elements found from Groups 3 through Group 12. So all the elements in here, some people consider these to be the transition metals. So these are the elements found in the d block, right? So we're talking about d orbitals here. So you have to understand electron configurations for this video. So that's one way to think about the transition metals, but that way is maybe a little bit too general sometimes. So there is another definition, which you'll find in the IUPAC website. IUPAC is an acronym for International Union of Pure and Applied Chemistry, and they say that a transition element refers to an element whose atom has an incomplete d subshell. So when you're talking about the d orbitals, we already know there are five d orbitals, and each orbital holds a maximum of two electrons. So 5 times 2 is 10. So 10 will be the maximum number of electrons that you could fit in your d orbitals, or your d subshells. So let's count that out on our periodic table so 10, so 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 for our d block. So let's go ahead and write an electron configuration for a transition metal and let's see how that applies to our definition from IUPAC. So let's write an electron configuration for iron. So here's iron right here. And if I wanted to write an electron configuration, let's say I wanted to do noble gas notation. So once again, I'm assuming that you know how to do this already so I won't spend too much time talking about it. But if I want to write a noble gas configuration, I would go to argon, which is the noble gas before iron, and I would put argon in brackets like that. And that takes me to the fourth energy level or the fourth period on the periodic table. And then just looking at the periodic table, I can say, oh, that would be 4s1, 4s2, so I can write 4s2 here. And then I'm in my d orbitals. So, again, just looking at the periodic table to write my electron configuration, I would say 1, 2, 3, 4, 5, 6 electrons. So that would be 3d6. And I could have written this 3d6 4s2. And right now, both are considered to be correct answers. And I won't get into a discussion about the order of filling of these orbitals in this videos. So I'll save that for another video. This video is only talking about definitions and identifying elements on the periodic table. And so either one of these would be a correct electron configuration. And when I look at the d orbitals for the electron configuration, I can see that there are six electrons in my d orbitals. Well, that's an incomplete d subshell, because I can fit a total of 10 into my d orbitals. And so iron would be an example of an element whose atom has an incomplete d subshell. So iron is a transition metal. Let's write the electron configuration for zinc. So let's find zinc over here, so right there on pour periodic table. So if I wanted to write the electron configuration for zinc, once again, I would go to the noble gas before it, which is argon. So I would put in brackets argon right here. And then, once again, it takes me to the fourth energy level. So 4s1, 4s2, so 4s2. And then I count over for my d electrons-- 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. So it would be 3d10. And once again, I could have written that argon in brackets 3d10 4s2. So it doesn't matter. So let's think about the definition for a transition metal, an element whose atom has an incomplete d subshell. Well, if I look at the d orbitals for zinc, they are completely full. I have 10 electrons in my d orbital, and so this is a complete d subshell. So this does not meet the definition for a transition element. Now, also in the definition, it talks about cations. So let's think about to the cation that zinc would form. Zinc would go to zinc 2 plus. So if I wanted to write the electron configuration for zinc 2 plus, I need to think about where does zinc lose two electrons? So if you've going from a neutral atom of zinc to zinc 2 plus, you would have to lose two electrons. Well, I already know that those two electrons are going to be lost from the 4s orbitals. So we're going to lose these two electrons right here on your electron configuration, and so you'd be left with 3d10. And once again, you have a cation that has a complete d subshell. You've completely filled your d orbitals, and so the cation does not have an incomplete d subshell, which means that it doesn't fit our technical definition for a transition element from IUPAC. And so, once again, there are two ways of thinking about it. One's a very general way. So you might hear someone talk about an element from Groups 3 through to 12 as being a transition metal, or you might find people who are a little bit more particular about the definition, who go along with IUPAC. It's good to be aware of both ways of thinking about it.