XcarvengerX said:
Some easy examples for you:
1H = 1s1
2He = 1s2
3Li = 1s2 + 2s1
4Be = 1s2 + 2s2
5B = 1s2 + 2s2 + 2p2
Just a note due to fussiness on the notation: we don't usually write electronic structures with + signs in between the orbitals.
Dreamerish*~ said:
Ohh, I get it now! That's not so bad...
Taking this a little further down the periodic table, you might also want to take note of the electronic structures of of Chromium and Coppper. If you follow the filling order, the EC you will get for Cr is:
Cr = [Ar] 4s
2 3d
4 ; and
Cu = [Ar] 4s
2 3d
9
However, there is also a rule (can't remember whose rule
) that says when the d orbital is half-filled or fully-filled the 3d orbital becomes lower in energy than the 4s orbital. In the case of Cr and Cu, one electron will "drop" from the 4s orbital to the 3d orbital, giving you:
Cr = [Ar] 4s
1 3d
5 -------> half-filled 3d orbital (two half filled orbitals)
Cu = [Ar] 4s
1 3d
10 ----------> fully-filled 3d orbital (a half filled 4s and fully-filled 3d)
Now you might be tempted to ask: what about Vanadium and Nickle?
Well, the same thing does not happen to those two elements. The 4s and 3d orbitals don't have a big difference in energy. It turns out that leaving everything just as it is is more favourable energy-wise.
Why am I telling you these? EC for Cr and Cu (along with Fe
2+ and other ions that are isoelectronic to Cr and Cu) are common exam questions
Have fun!
Edited