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Topic: naming d-orbitals?  (Read 7474 times)

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polaris

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naming d-orbitals?
« on: December 29, 2005, 04:04:22 PM »
im still not sure how you know the charge for the elements in the d-orbital...transition metals?

i think you have to use orbital notation but im not sure how to use that either!  

can someone please help me? and give a few examples too please!
« Last Edit: December 29, 2005, 04:05:51 PM by polaris »

Offline Mitch

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Re:naming d-orbitals?
« Reply #1 on: December 29, 2005, 04:11:09 PM »
give an example
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kclive

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Re:naming d-orbitals?
« Reply #2 on: December 29, 2005, 07:50:43 PM »
This is gonna be kinda hard to type but...

Here's the electron config of chromium:

1s22s22p63s13p64s13d5

And this is the shorthand version, of course:

4s13d5

So basically the orbital notation would be:

?  ? ? ? ? ?
4s    3d

I tried to put underlines beneath the arrows but it didnt work. The underlines that were supposed to be there indicate separate orbitals. Thats how you do orbital notation for d-orbitals.

The one catch with transition metals is that they promote an electron from the 4s (or whatever outer s-orbital they have) to the previous energy level's d-orbital. According to the rules, the 3d sublevel is only allowed to have 4 unpaired electrons since 4s must have 2 electrons. But in order to avoid repulsion in the outer levels so as not to lose an electron, an atom such as chromium would have all unpaired electrons in the outer sublevels.

But I cant find the place in my class notes where it says which transition metals promote electrons. Could you please help me with that one? Thanks!

Glad I was able to help you out, polaris. ;)
« Last Edit: December 29, 2005, 07:51:10 PM by kclive »

Offline jdurg

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Re:naming d-orbitals?
« Reply #3 on: December 29, 2005, 08:08:00 PM »
What you can try and do is just count out the number of electrons that the element should have in it's normal configuration.  Knowing that the 3d and 4s levels are almost equal in energy, you'll see what the appropriate configuration should be for the electrons.  Electrons like to be paired, but they don't like to be crowded.  So if electrons can be moved around to align themselves up properly they tend to do so.  The problem is, there isn't a 100% always followed law for the electron filling, so in some cases you just need to remember the 'odd ones'.
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polaris

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Re:naming d-orbitals?
« Reply #4 on: December 29, 2005, 08:18:41 PM »
thanks for the help but why does chromium have

4s1 3d5

instead of

4s2 3d4?

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Re:naming d-orbitals?
« Reply #5 on: December 29, 2005, 08:45:11 PM »
Because a half-filled d-subshell lowes the energy more than a filled s-subshell.
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polaris

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Re:naming d-orbitals?
« Reply #6 on: December 29, 2005, 08:58:54 PM »
well than...is the charge on chromium a 2+ because it loses the s electron?   ???

Offline jdurg

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Re:naming d-orbitals?
« Reply #7 on: December 29, 2005, 09:26:51 PM »
well than...is the charge on chromium a 2+ because it loses the s electron?   ???

Think about what you're saying there.   ;)  If it loses ONE s electron, what charge would it have?  Charge is determined by the number of electrons compared to the number of protons, not on where the electron comes from.  So if Chromium loses one electron, then it will have an arrangement of 4s0 3d5 and a charge of +1.  While chromium does have an unpaired 4s electron just as potassium does the 3d5 electrons, which are further away from the nucleus than the 4s1 electron is, are able to shield that lone 4s1 electron and prevent it from reacting as readily.  Potassium doesn't have that buffer which is why it will react readily and chromium will not.

In a similar manner, Gold has an unpaired 6s1 electron just as cesium does, but gold has 4f and 5d electrons there to keep it from reacting as readily as cesium.  It's really pretty neat when you see these "oddities" in the electron filling and then see why that happens and be able to predict what ions it will readily form.
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