Of the two metals, which is least reactive?

[csx]

to answer this you use closed/half closed shell to find your answer.

The answer choices were Mg or Cu.

I said Mg because its shell is closed. The real answer is copper though.
Mg's elect. config is: [NE]4S2
While Cu is: [Ar]4S1 3D10

doesnt the lack of pairing in the 4s orbital also make it paramagnetic.

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[Cawolf]

I just want to note that the metals copper, silver, gold, and platinum are highly nonreactive and that is why they are precious - as a shortcut to producing an answer.

 

[justadream]

@csx

I believe I read somewhere (probably TBR) that having closed d orbitals is better than having closed s orbitals.

Also, just know that elements in the first 2 columns are often reactive.

 

[techfan]

I think it might have to do with having the 3d subshell full which it more stable. If I'm not mistaken the protons (since as you go across the periodic table you are adding a new proton to the nucleus for each electron) are pulling in the electrons in to make it more compact (why the 3d subshell is inside of the 4s). Someone correct me if I'm wrong.

 

[csx]

@csx

I believe I read somewhere (probably TBR) that having closed d orbitals is better than having closed s orbitals.

Also, just know that elements in the first 2 columns are often reactive.

this would make sense as I know the 4s gets bumped up to the 3d to make 3d10. It doesn't do that for no reason.

 

[GoldenTuth]

Regardless of shells, (why even go there) it's obvious that alkali and earth alkali are more reactive, touch it with your bare hands on a nice humid summer afternoon and it will blow up in your face, while copper will maybe oxidize in a few months

 

[kraskadva]

to answer this you use closed/half closed shell to find your answer.

why?

The answer choices were Mg or Cu.

I said Mg because its shell is closed. The real answer is copper though.
Mg's elect. config is: [NE]4S2
While Cu is: [Ar]4S1 3D10

All elements want to be noble. Keep that in mind.
So, Alkali and alkali earths like to give up their s-shell e- to get to the noble gas config.
Halogens like to steal an e- to get to the noble gas config.
These groups can fulfil their nuclei's desires pretty easily, since they don't have far to go. So they're more reactive. They'll go for what they want immediately.
As you move closer to the middle of the periodic table though, more e- have to be lost or stolen to get to that ideal configuration, so it doesn't happen quite as easily. Hence they are less reactive. In the middle especially, they wallow in indecision (dump or steal, dump or steal) and can go either way or neither way.

doesnt the lack of pairing in the 4s orbital also make it paramagnetic.

...Mg doesn't have a 4s shell...and it has 2 e- in its 3s shell...and s shells only hold 2 e-...so it is paired. And diamagnetic.

 

[calisurfer19]

So I got this question wrong initially too b/ I was thinking higher energy = increased instability. The thing that helped me out w/ reasoning here is asking myself which molecule takes the least effort to complete its outer shell? Mg needs to have electrons taken away from it, but copper can just make an internal shift. Loved the analogy that someone said about gold, copper, and silver - I actually use this to my advantage when refining gold and silver. Shoulda put two and two together