Transition metals: why not anions?

[David513]

Perhaps this is a completely silly question but I was wondering today why transition metals never form anions. For example, it seems like copper would love to take on one additional electron to fill its subshell, no? Can anyone tell me why it is that transition metals never form anions?

Thank you!

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[bunchesonothing]

Perhaps this is a completely silly question but I was wondering today why transition metals never form anions. For example, it seems like copper would love to take on one additional electron to fill its subshell, no? Can anyone tell me why it is that transition metals never form anions?

Thank you!

Look up periodic trends. They're far more likely to lose electrons.

 

[Ad2b]

Cu always has a + charge, meaning it has too MANY electrons to start with... it will never take another one unless it converts from Cu+ to Cu 2+

Remember: the + means how many EXTRA electrons it's carrying, not how many it can take on ... which is ca+ion (see how that works?)

An-ons are missing an electron ... Cu will never have that issue unless, possibly, it's in a nanosecond transition state ...

Also, if you have NOT mastered the orbital shell filling gunk of gen chem, now would be a good time. As orbitals don't fill necessarily 1-2-3-4. In fact, they fill 1s2, 2s2, ... then 3p fills before 4s so there's extra electrons floating around.

Here's a link to help you: http://chemistry.stackexchange.com/...o-form-positive-ions-instead-of-negative-ions

 

[bunchesonothing]

I find the above post kind of confusing.

My understanding is that having a + just means that there are more protons than electrons in an atom, making it non-neutral. I don't think that it necessarily means there are too many electrons. If Cu 2+ takes on another electron it becomes Cu +, not the other way around. The propensity to lose electrons is what makes something prone to being a cation.

Metals, etc on the left side of the periodic table have lower electronegativity(desire to retain and gain more electrons). As a trend, they're happy to lose electrons to make their complete octet. Nonmetals, on the right side, are more electronegative. They are prone to becoming anions. Anions have more electrons than they do protons.

 

[rsrs3739]

I find the above post kind of confusing.

My understanding is that having a + just means that there are more protons than electrons in an atom, making it non-neutral. I don't think that it necessarily means there are too many electrons. If Cu 2+ takes on another electron it becomes Cu +, not the other way around. The propensity to lose electrons is what makes something prone to being a cation.

Metals, etc on the left side of the periodic table have lower electronegativity(desire to retain and gain more electrons). As a trend, they're happy to lose electrons to make their complete octet. Nonmetals, on the right side, are more electronegative. They are prone to becoming anions. Anions have more electrons than they do protons.

Yep Ad2b has it backwards. Positive ions have more protons than electrons, as indicated by the plus sign and negative ions have more electrons than protons as indicated by the negative sign. For example, +2 means the atom carries 2 more protons than electrons.

 

[Ad2b]

yep - brain fart - was in the midst of scurrying through my spring books - thanks for correcting me!!!

 

[David513]

Thanks for the replies so far.

Unfortunately, I still don't feel like I understand why copper wouldn't form an anion in any situation. Its configuration is [Ar]3d^10 4s^1 and its electron affinity is in the mid-range. So why wouldn't it ever take on an additional electron to form a complete s subshell becoming [Ar]3d^10 4s^2 , i.e. Cu-, as opposed to what we know it to do which is form a complete d subshell becoming [Ar]3d^10 , i.e. Cu+ ? It seems like we would see Cu- at least SOME of the time, no?

 

[fittycent]

.

 

[ElectricNoogie]

From some Chem experts, hope this helps:

Here are the outer configuration of some transition elements:

• Sc: [Ar]3d14s2
• Cr: [Ar]3d54s1
• Co: [Ar]3d74s2
• Cu: [Ar]3d104s1
• Zn: [Ar]3d104s2

As you may notice, they can form ions by either losing or gaining electron in 4s orbital. In the chemistry of the transition elements, the 4s orbital behaves as the outermost, highest energy orbital. When these metals form ions, the 4s electrons are always lost first, leading to a positive charge on ion. Gaining any electron in 4s orbital would decrease the stability of anion thus formed. So, they form only cations (positive ions).

In general, the outer electronic configuration of transition elements is ns2(n−1)d1−10. Because of reasons above, the electron removes from the ns orbital, where n = principal quantum number of atom.

See Zn2+ configuration: [Ar](3d)10 as an example. The electron exits from 4s orbital, leading to the formation of a positively charged ion.

 

[JoeCaputo]

Electron affinity

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[vivatix]

From some Chem experts, hope this helps:

Here are the outer configuration of some transition elements:

• Sc: [Ar]3d14s2
• Cr: [Ar]3d54s1
• Co: [Ar]3d74s2
• Cu: [Ar]3d104s1
• Zn: [Ar]3d104s2

As you may notice, they can form ions by either losing or gaining electron in 4s orbital. In the chemistry of the transition elements, the 4s orbital behaves as the outermost, highest energy orbital. When these metals form ions, the 4s electrons are always lost first, leading to a positive charge on ion. Gaining any electron in 4s orbital would decrease the stability of anion thus formed. So, they form only cations (positive ions).

In general, the outer electronic configuration of transition elements is ns2(n−1)d1−10. Because of reasons above, the electron removes from the ns orbital, where n = principal quantum number of atom.

See Zn2+ configuration: [Ar](3d)10 as an example. The electron exits from 4s orbital, leading to the formation of a positively charged ion.

I have a question on a similar topic.

So when transition metals lose electrons to form cations, are they never able to achieve a noble gas configuration? So, would a transition metal cation be less stable than cation of other metals like alkali metals and alkali earth metals that are able to reach a more stable noble gas configuration?

 

[David513]

Wow, thanks for the reply @ElectricNoogie ! That was exactly the answer I needed. I guess because maintaining a full 4s shell and a full 3d shell would be a higher energy, i.e. less stable, state than only a full 3d shell, copper doesn't ever take on electrons to become an anion. (And then the reason that chalcogens and halogens, for example, do take on electrons is that they get to form that snuggly noble gas configuration, so they DGAF about snatching up others' electrons cause they're all about that noble gas, stable lifestyle.) Thank you!!

@vivatix My educated guess is that you are correct: a transition metal cation is almost certainly less stable than alkali or alkaline earth metal cations because of the transition metal cation's lack of noble gas configuration.