What is the correct electron configuration for copper?

[DrOnline]

Homework Statement

I'm a complete chemistry novice, just on chapter 1 of my book here.

I am tasked with writing down the electron configuration of Copper, atom number 29.

Homework Equations

I've got my orbital chart here. 29 electrons to fill in.

The Attempt at a Solution

I go with:

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁹

On my chart, and I am sorry if I am making a mess of the terms of chemistry here, it shows 4s filling up before electrons fill up 3d.

And this is correct according to my school book.

So I try to draw it using the normal onion layer model.

2-8-17-2

Then I got wikipedia, and it shows this picture:

2-8-18-1

Is my book wrong? Am I wrong? Is wikipedia wrong here?

 

[mfb]

Those metals can look differently - as Wikipedia has a list of those exceptions, I would expect that 4s¹ 3d¹⁰ is right.

 

[DrOnline]

Oh wow. Ok. Thanks!