electron shell filling/ionization order discrepancy

[AlexB]

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Hi,
So, I am mainly wondering why there is a difference between the electron shell filling order of an element vs. the order in which electrons are lost.

A good example is TBR Gen chem Pg. 131, Q: 25.

Elements fill in the order 1s2s2p3s3p4s3d etc. etc.

However, in this question, we have ions. Take manganese for example.

Neutral Mn= [Ar]4s2 3d5
Mn+2 = [Ar] 3d5

This is opposite the filling order, no?

 

[Phantastic]

An analogous example would be the half-filled and fully-filled d orbitals, whereby an s orbital electron of the same valence shell is promoted into a d orbital spot due to the lower energy of this configuration.

So yes, electrons do configure themselves into the lowest available energy, and aufbau and hund's are great rules for figuring out in what order...but there do exist exceptions.

 

[lesset01]

However, in this question, we have ions. Take manganese for example.

Neutral Mn= [Ar]4s2 3d5
Mn+2 = [Ar] 3d5

This is opposite the filling order, no?

This really isn't "filling order" as much as it is the order that the electrons are lost. When a neutral atom loses electrons, it loses them from the highest energy orbital first. So in the case of neutral Mn losing e- to become Mn2+, it will lose e- from the 4s orbital first (not the 3d orbital) because its higher in energy.

Hope this helps! 😛

 

[AlexB]

This really isn't "filling order" as much as it is the order that the electrons are lost. When a neutral atom loses electrons, it loses them from the highest energy orbital first. So in the case of neutral Mn losing e- to become Mn2+, it will lose e- from the 4s orbital first (not the 3d orbital) because its higher in energy.

Hope this helps! 😛

Thanks!!!